Hello. I'm playing the Rewind Upsilon modpack for 1.4.7 and tried to play CCDoom as a joke when streaming my game to my friend, and noticed that the inputs got stuck. Other than that, the game seemed to work completely fine. Seems like the only thing missing here is the key_up event.
I don't remember if the event was available in this version originally, but it would be nice to have as newer software depends on it.

My test program:

Test program output (no key_up events!):

I am using 1.115.1 of the CC:Tweaked coremod for 1.4.7.