After you run an FSDT update, the first startup GSX will rebuild its own internal model cache, which can take a variable and not predictable amount of time depending how fast your system is, how big your Community folder is and how fast the disk the Community folder is and if the antivirus is slowing it down because you haven't added the Community folder to the antivirus exclusions.
Normally, it doesn't take more than 10-15 seconds to rebuild the models cache but, if it takes longer than the maximum amount of time the menu is retrying, it won't keep retrying forever, so you just need to open the menu again.
If you restart Couatl but don't wait enough for the model cache to be rebuild, so you restart it again, you are forcing rebuilding it again, and again, because each time you restart it after an update, it will restart the rebuild process from scratch until is completed, so if you keep restarting it will never complete.
This means, after an update, you just have to wait more before trying a restart.