Doesn't it seem unlikely that the SSDs are bad for all of us. And blaming on SSD doesn't explain why MC 18 was working and not MC 19. Also, if SSD is bad, since it is the system drive, wouldn't that make the OS itself unstable...
Regardless, here is a very interesting result:
To start with I can put JRiver into hang requiring force close every time by just playing music for 10 minutes or so then attempt to close the program. It doesn't matter whether from theater view or standard view.
On a hunch I made a new backup of the library, then restored from that same backup. So there should be zero net change. Immediately, I am unable to put JRiver into hang state. Now, I continue to use JRiver, play music for a few hours, open and close the app a few times, and after a while I close JRiver (as a test) and it goes into hang state, needing to be force closed. A while later and it hangs every time I try to close it, after playing music for a 10 minutes or so. At that point I try restoring the library again. And again I am not able to put the program into hang.
Is it possible that there is some corruption going on which is somehow cleaned up during the backup and restore process but that accumulates over time to the point where it causes the program to hang?