When starting UE from command line and passing a file as argument, UE opens and loads that file, also highlights the title of the window (file name), but the current window displayed is that of another, previously loaded file. The window of the file displayed and active (i.e. accepting keyboard inputs) is not highlighted. 

Illustration with a simple example:

• 3 files are open from a previous session (aaa.txt, bbb.txt, ccc.txt). 
• UE is invoked with 4alias.nt as a parameter.
• when opened, bbb.txt is the active window (even though as per the file tabs it should be 4alias.nt)

I can't say when this behavior started, but I am sure this was not like this in the past.
(It's not that the command prompt is my home, but the same happens when invoking UE from programs like File Commander.)

Has somebody noticed this as well? Any suggestions?

Thanks for picking up the ball, Mofi.

I'm using the most recent version for Windows (27.10.0.148).
See attached screenshots for the settings you've asked for.
This is the command line call:

Thanks for the additional information regarding to used version of UltraEdit and the configuration settings.

I could reproduce the issue with 32-bit UltraEdit v27.10.0.148 with your configuration and having opened the same files as you on exit with active file being the file bbb.txt on exit. UltraEdit restores the workspace on next start with this configuration and so the file bbb.txt is the active file after restart as on last exit although file 4alias.nt is opened additionally according to the command line argument.

The issue is that the file tab of file 4alias.nt indicates that this file is the active file while in real file bbb.txt is the active file with having checked Dockable tabs at Advanced - Settings or Configuration - Application layout - File tabs - Operation.

This file tab issue does not occur with having unchecked this setting in the configuration dialog or via file tabs context menu File tabs - Dockable which is the default configuration. Further, it does not occur if the file 4alias.nt is specified on command line with full path.

This is a bug in my opinion with enabled Dockable tabs which I report by email to IDM support.

@Mofi   

Many thanks for this hint! 
Indeed, using the full path name  seems to make a difference. I have changed the external editor string in my "commander" application accordingly; let's see if this entirely removed the issue.