I have noticed this after the supplemental update 10.15.4 on 4/8/20. It seems that either Finder, Activity Monitor, Safari, and in my case, also McAffee Internet Security/Total Protection have all been noted to be "Not Responding".
The only way I was able to shut down my 2018 15"MBP i9 was to force power down by holding Power button down.
My solution that I found so far- albeit only a few hours ago- power down. Power on and boot into Recovery Mode: Command + R. You may need to enter Firmware password if enabled.
Launch Disk Utility. Run First Aid on all your partitions. For me: MacOS, MacOS data, and boot up (don't recall the exact wording). MacOS and boot up partitions were ok. The data one found several mis-matched data to my 16 Time Machine snapshots.
After fixing them, exit and reboot.
So far- so good. "knock on wood"