I've been using MC since MC20 and have used almost all of the major versions in between 20 and 30. In terms of stability, MC has been very stable. For a while, on one piece of hardware, I had some audio dropouts. But haven't had that in 6 or 8 years now.
MC only "freezes" on me when drives are asleep. Then, after a pause for the drives to wake up an begin responding, MC becomes responsive again. This generally only happens on first startup of MC. I use ALL local drives. Nothing on the network.
I suspect that your network attached drives are not available during some periods. They are probably going to sleep and the NAS is not able to deliver data from those files until the drives wake up. This is just a theory.
To test it, you could have a Finder window that you use to see if you can get a directory listing of the network drive where your music files are located. Try to list the files when MC is being unresponsive.
How are you mounting the files from the NAS to your Mac? Windows file sharing (SMB)? Mac native file sharing? NFS? DLNA?
Brian.