Breaker trips in one circuit but not the other
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.