I'm having the same problem. Apps don't launch. I have a health care app that is critical to my wellbeing that I must use every few hours. I tap the icon and the app opens then immediately closes before anything is output to the screen. I check storage and over 1/2 of the 128Gb is used by system and other, the grey on the bar graph. I follow the step prescribed here and free up 10-20Gb. The app works fine. The next time I try to use it, I have to repeat the whole process. When I start the app, the system should return enough cache storage to let the app run. It seems the memory manager isn't doing it's job.
I have seen 127.7Gb used, cleared up system/other and gotten it down to 120Gb. Then, as I watch it, doing nothing, usage goes up to 125, drops to 122, then go over 127 again.
What I would like is to set a lower limit on available storage, say 1-2Gb, after which the system will start returning cache. As it is, it seems the current threshold for returning memory is too low.