here's a hopeful good one for you to figure out. I got Entrenchment installed and opened the game through Impulse. Normally I don't run games through Impulse, I just start the game with the .exe file.
Played the game for about an hour. Minimized the game app and left it running. While it was running in a minimized state, I closed Impulse. Then I closed the game app about 1/2 hour later.
Couple of hours later, I opened Impulse and both the Entrenchment and the original Sins games were un-installed and showed that they were available for install. I tried to start both through Impulse and through the .exe and got an error statement about fmod.dll not found. Had to re-install both games completely again.
Don't know if it had anything to do closing Impulse down why the game was still running after I had it started through Impulse or not, but thought that I'd let you know anyways.