This usually doesn't happen, but it's been occurring more often with MCreator 1.9.1, and the the problem is simply this: I run the client to test a mod I'm working on, I play around a bit, see what needs to be fixed, but then when I hit 'Quit Game', my mod workspace is just frozen saying that it is still running Minecraft. I originally thought this happened because I was exiting the game too fast, but it really isn't. When this does happen, MCreator is unable to be closed, the mod cannot be edited, and it lasts for about 20-30 minutes before Gradle realizes that it has nothing to run. Whether it's a Gradle or MCreator issue, I'm not sure. But please look into this as it is very annoying, thank you. (I take that back, it's a lot longer than 30 minutes...)
Issue comments
This most likely happens due to one of the procedures calling itself, for example, an entity that has a trigger on hurt and that trigger calls explode procedure block which in turn hurts the entity again.
Try getting it to crash while the console tab is open to get any logs.
I haven't tried making it crash yet, but I just noticed this and want to make sure that it's supposed to say this:
Starting a Gradle Daemon, 1 incompatible and 1 stopped Daemons could not be reused, use --status for details
This mapping 'snapshot_20171003' was designed for MC 1.12! Use at your own peril.
What are the contents of the console tab when MCreator still thinks the gradle is running?