I know you are to avoid making statement based on opinion, so here is my thought.
The Breaker, like me, has gone soft and infirm.
The 'thermal' part of the thermal-magnetic breaker was willing to tolerate the slow death of the burned switch, but it weakened itself in the process. So the slightest load will now trip it.
Your power conditioner has a ground fault
But it does not have an arc fault.
That is why it is failing on a combo GFCI-AFCI but not failing on an AFCI only.
The fact that it doesn't trip with the ground-removing cheater proves it is a fault involving the ground wire. That is, it is not a fault to a water pipe, cat, etc.
Now, did the conditioner work with the ground-removing cheater? If its own internal loads now do not work, that means its internal loads are drawing from hot and returning to ground, which you have severed. They should not do that. If the internal loads still work, that doesn't tell us so much.
The fact that the conditioner fails alone on the wire, with only its own tiny load operating, suggests to me that it's a hot-ground fault.
It needs to flow 8ma to trip the GFCI, and the conditioner's own loads should be quite small. It may have a new hot-ground fault due to a short inside the machine, which is separate from its own loads. That could be any value.
Or, it could have a neutral-ground fault due to bad design or a different short. With a neutral-ground fault, power returning to source has 2 choices, and flows down both in proportion to their conductance (1/resistance). Anyway, since current is flowing both paths, one of them correct, it takes more than 8ma to trip the breaker.
Best Answer
The only interesting information here is how many amps were being pulled on the circuit at the time the breaker popped. Breakers actually trip on heat, and a sign of a malfunctioning breaker is random inexplicable opening (tripping).
You could get yourself an Amprobe and watch it while a 'helper' turns things on and off and simulates normal activity in the room to see, however more than likely one of two things is going on:
So, if you go the Amprobe route, you have to be there just at the right time to catch it. The event causing the breaker to trip might be happening fast enough for the tester you have not to notice it.
Replace the breaker (or have it replaced) first and see if the problem goes away. If it doesn't - figure out what's coming on at that interval that might be causing it. If the problem persists and nothing is suspect, have an Electrician take a good look at it, you probably have feeder somewhere that comes into contact with ground randomly.