I have over 21,000 QuickTime videos stored a file server. (I own and operate a film/video archive.) I have used and relied on QuickTime 7 for over 15 years and currently use it on a 2018 Mac Mini running Mojave. A few days ago, I noticed QuickTime 7 has started to self-quit after some heavy use, and I get the bug report screen. I don’t think QuickTime 7 ever crashed before. There is also one new problem I have seen. Sometimes, video files (2880x2160 Apple ProRes 422HQ) will play back with flickering yellow frames. QuickTime X plays them back just fine. Something in the OS has changed - wish I knew what it was.