I have a number of devices connected over wifi and some connected wired. None of them are moving and I can see on the clients every few minutes the wireless connection is disconnected for a few seconds then reconnects. This happens even if they are actively streaming data.

I have another access point set to DHCP client but just in case I shut that one down and saw no improvement. Some of these devices are in the same room as the router and have a signal ~-55.

I will sometimes see log entries like this: I bashed my head into it awhile and nothing I seem to do improves the situation. I'm kind of at a loss for even understanding what is going wrong (other than "devices disconnect and reconnect over wifi). Any suggestions as to where I should look?

I had similar problems on older v7.x and reverting to previous version solved problems (v7.15.x works...).

Than again, I have had problems with "default config" before. Sometimes, somewhere something is left "on default config" and it makes problems. Not that I have seen something in your file like that.

If reverting to older version does not help, I would suggest reseting it all, without default config and starting from scratch. I do understand you did many thins to the router, but it is not such a big job to get it all back. Even better, you can import line-by-line from rsc file if it is too much to type it all.

Finally, sometimes, during upgrading to new version something breaks. It happen to me before once or twice, but not recently.

... hope it helps.

Any suggestions as to where I should look?

Try disabling WPA3 and Management Protection on WiFi/security for every wlan interface
I was experiencing exactly the same disconnection problems until I left only WPA2 enabled and disabled management protection.
Don't ask me why this problem is occurring with ROS (other routers work fine). I love Mikrotik devices and RouterOS but they are really PITA on WiFi.

Disabling WPA3 is probably a good idea.

This is wifi, this is invisible radiation. Destructive Interference followed by disconnects is always possible, and can never be found by looking at the configuration.
I have reproducable cases where good signals (eg -55dBm, 98%CCQ) deteriorate if another "strong emittor"device (Mobile Hotspot, Chromecast, extender repeater ....) comes close to the AP.
The interfering device is on other channels in the same band. Expected to just coexist as the channels do not overlap.

- however existing good connections on that AP drop
- new connections with RADIUS authentication fail on that AP
- interfering device is nowhere in the registration table or in the log of that AP (eg like associating)
- wifi SCAN will not find that strong emittor , unless it sends beacons (what it mostly does not)
- Snooper shows them when they are associated with another AP

Problem is repeatable. It cannot be fixed with modifying the config. Rejecting the strong transmitter in the access list does not help (it does not associate or try to connect with the AP) Move them further away , and in my cases disconnect problems were gone. Wifi destructive interference has many variations. It's something to try out. It might help in some cases. Your mileage will most probably vary.

Smartphone and tablet need to be 15cm away from a hAP ac2 even if they only connect with other APs . laptop 30 cm. 20 dBm sending devices at 1.2 meter as a strict minimal distance !!!
Some have 5 of those repeater/VPN-box/extender/Mifi router in their travel case.