when an existing sublime_text.exe process is elevated(launched from admin cmd using subl). Then further subl.exe from any non elevated cmd will fail to open any files. subl.exe silently terminates. Is it completely impossible to workaround this because of Windows UAC architecture? (may be why not open a non elevated sublime_text.exe process instead of silent subl.exe termination).
Sublime Text seems to try to reuse the existent instance, but as it has high level privileges, a non high level process cannot interfere with it. You could try to use the flag
--multiinstance. Or create a portable version of Sublime Text to run a administrator and let you installed Sublime Text version to handle opening files.