Reported on issue 15230. Resizing your ThinLinc session with this command active: tl-run-winapp-seamless notepad.exe results in another instance of notepad getting executed. Since RDP doesn't support resizing a session, we reconnect whenever we need to resize. It seems like we resend the spawn command to seamlessrdpshell when this happens. Hopefully just a matter of clearing out those variables once we've sent the initial command.
This is now fixed in upstream commit 1809.
Brought to ctc in vendor drop 29021.
Looks good, I am not able to reproduce the problem with build 4506 on windows 2008 r2.