Due to local network issues I've had to lock my S22+ to only use a 5G band (N71 SA)

This is working great, except fairly frequently the phone simply disconnects from the network for no apparent reason for a few seconds at a time.  No change in signal strength is noted... it can have 5 bars of 5G showing then suddenly disconnect for a couple seconds then reconnect.

Anyone know why it's doing this and/or how to prevent it?

Oddly, if I turn the screen off when the 5G disconnects it doesn't reconnect unless I turn the screen back on.  Was thinking maybe some sort of battery saver feature... but the app I'm using is exempted from  battery management and 5G is cutting off even when on AC power.