Finder becoming unstable after losing wifi connection to NAS

I have a strange problem. I have a NAS at home. Typically, I mount to it from the wifi connection. Lately, if I neglect to unmount it, of if I move from one wifi hotspot in my home to another, or sometimes if I just close the my MBP for an extended period of time, I run into a problem when I start using the machine again. Finder locks up and wants to be relaunched, but relaunching does not work. The mount points remain visible, but are not accessible. The system eventually restarts.

I don’t know for certain that this problem has anything to do with the mounted network volumes, but that seems to be the culprit. I’ve had this NAS for over a year and have never seen this problem before.

Any idea about what I can do to avoid this—excluding the obvious of being more careful to unmount. Or is that the only solution? This seems like a severe consequence for failing to unmount.

MacBook Pro 15” (2015) 16 GB RAM
Asustor NAS (6TB Raid 5)

I’m not sure what might have changed.
Which protocol are you using, SMB, or AFP?
Synology suggests using SMB, as it is more robust than AFP.

SMB. Thanks. For whatever it’s worth, I have not been (Knowingly) tinkering with any network settings involving the NAS.