how old are the UPS units, after a few years 2 or 3 the batteries go
bad and the units act wierd.Espically bad on small UPS units like those
40 buck units

I have a couple doing that here.

DEFINETELY GET RID OF the FPE panels its a fire waiting to happen!

Put a voltmeter on the line, sometimes minor fluctuatins appear large
to certain lamps. I had some cheap fluroscent shop lights that acted
wierd with a 2 volt drop, a trivial change.