In more than 10 years nobody has ever reported such an unexpected behavior of UltraEdit in user-to-user forum.

Is the caret really at line 1 column 1 when this happens, i.e. like Ctrl+Home is pressed?

Do you have the document map visible and unintentionally perform a click on it with resulting in scrolling to top?

What actions do you have configured for the mouse buttons other than primary (left) and secondary (right) button?

Has your PC a touch pad or a touch screen and you execute by accident the gesture to execute moving caret to top of file?

I suggest to look on mouse / touch pad / touch screen settings and which actions / gestures are enabled on which you are not aware of.

You might check the UltraEdit setting Disable drag & drop at Advanced - Settings or Configuration - Editor - Miscellaneous and see if that makes a change.

Do you have any macro file configured for being automatically loaded on startup of UltraEdit which contains one or more macros with hotkeys/chords assigned containing the command Top or Key Ctrl+HOME?

Do you have scripts added to scripts list with hotkeys/chords assigned containing a command moving caret to top?

Open Advanced - Settings or Configuration - Key mapping, click on button Show key mapping in editor, close configuration with button Cancel and look line by line on created text file with all the currently active key mappings including macros and scripts.

Ah, okay, you use key Divide on numeric keypad. Most keys on numeric keypad have two different key codes depending on keyboard layout and state of Num lock.

For example on German keyboard with Num lock not enabled the key codes of following key changes:

1 ... End
2 ... Down arrow
3 ... PgDn
4 ... Left Arrow
5 ... Clear
6 ... Right Arrow
7 ... Home
8 ... Up Arrow
9 ... PgUp

So I suggest to press Ctrl+Divide with Num lock enabled and selected code. Next disable Num lock and press once again Ctrl+Divide. If this is resulting in moving caret to top of the file, then alternate key code for Divide on numeric keypad is Home on your keyboard.

Just to be 100% sure: You are using this Swedish keyboard which is very similar to this German keyboard?

I prefer German IBM (same hardware).

And you do not accidentally switch input language for active application (UltraEdit) by key as described for example by article 3 Ways to Switch Input Methods on Windows 10?

Pressing Alt+Shift and leaving the two keys without pressing any additional key switches the input language for the currently active application if multiple keyboard layouts (input languages) are installed as by default for non US countries. In Windows task bar there is the two or three letter input language indication. I have seen many people in Austria switching by accident with key the input language for active application from Germany (DE or DEU displayed on Windows task bar) to English US which is always also installed by default (EN or ENU displayed on Windows task bar) and wonder why some keys do not work as expected in active application while in other applications (DE/DEU displayed on Windows task bar after switching to other application) the same key works as expected. Whenever I was asked for help on this issue, I solved it my removing all other input languages (keyboard layouts) than the one really used by the PC user according to used keyboard which disables the hotkey to switch input language as there is not anymore a second one.

I suggest next to open Graphic Settings by right clicking on a free area on Windows desktop and left click on this context menu item. This action opens the graphic settings application of installed video adapter driver/application suite. The installed video adapter driver/application suite has usually an Options and Support item on which a Hot Key Manager can be customized. The hot key manager is an application installed with video driver running in background to perform display related actions on pressing certain hot keys. I don't expect an effect by these hot keys with UltraEdit, but better cross-check the hot keys set by the hot key manager of used video adapter. I have them all disabled on my PCs as I never use them and disabled also start of the hot key manager program on startup of Windows to decrease Windows startup time.

Further I suggest to click on Windows Start button on using Windows 7, click into edit field Search programs and files, type msconfig and execute this Microsoft application. On Windows 8 and later Windows versions open Task Manager with Ctrl+Alt+Del or by right clicking on a free area of Windows task bar and clicking in context menu on Start Task Manager. In started System Configuration or Windows Task Manager click on tab Startup. You can see now which applications are started on Windows start and you can uncheck them. I suggest to uncheck all with exception of anti-virus/anti-malware application, click on button OK and restart Windows. Then work some days with UltraEdit without all those applications started usually during Windows start and see if that makes a difference. You can re-enable any startup of an application at any time the same way as on disabling it in case of missing a feature you use often which requires that one of those applications currently not anymore started automatically needs to be started on Windows start.

There is also free Autoruns of Sysinternals (Microsoft) which lists really everything loaded or started on Windows start including services and drivers if you are interested in.

Okay, application suite for Intel and AMD video adapters have a customizable hot key manager, but not the Nvidia application suite as far as I could find out with some quick internet searches. Nvidia 3D Vision seems to define hot keys, but not easy customizable for a user according to blog Modifying all 3D Vision control key combinations as you need. I think, we can forget this potential source for the problems. The Nvidia application suite is most likely not the source of moving sometimes unexpected the caret to top of file.

I get more and more the impression that an unknown multi-key assignment not listed in file uedit64u.uek could be the reason for this very hard to find issue.

I suggest following:

1. Exit all running instances of UltraEdit.
2. Open the folder %APPDATA%\IDMComp\UltraEdit in Windows Explorer or your favorite file manager.
3. Rename the file uedit64u.shortcuts.txt for example to UltraEdit_Shortcuts.txt.
4. Delete the file uedit64u.uek and all other *.uek and *.kbd files still existing perhaps from older versions of UltraEdit.
5. Start UltraEdit, open Advanced - Settings or Configuration - Key mapping and customize once again the key assignments.

The button Show key mapping in editor can be used to recreate uedit64u.shortcuts.txt after key mapping customization. This file should be compared with UltraEdit_Shortcuts.txt to verify if no customization was forgotten on redoing the key mapping customization.

I recommend on key mapping customization to avoid that Ctrl+P is used for command Print and chord Ctrl+P, Ctrl+S is used for command Persistent selection. This is the default key mapping of both commands, but I think, this default is not good. Better would be to use for Persistent selection something unique like Ctrl+Shift+E or Ctrl+Shift+L.

Please note the following commands as listed in file uedit64u.shortcuts.txt with Num lock not enabled:

• Alt+Subtract ... Position active line at top of window ... Alt+<Num>−
• Alt+Clear ... Position active line at center of window ... Alt+<Num>5
• Alt+Multiply ... Position active line at center of window ... Alt+<Num>×
• Alt+Add ... Position active line at bottom of window ... Alt+<Num>+
• Alt+Left Arrow ... Position cursor at previous paragraph start
• Alt+Right Arrow ... Position cursor at next paragraph start
• Alt+PgUp ... Position cursor at top of window
• Alt+PgDn ... Position cursor at bottom of window

Alt+PgUp can be the same as Ctrl+Home if the first displayed line is the first line in file.

And of course pressing Ctrl+G, 1, Return or Enter moves cursor also to top of the file.