Rotax 582 engine problems

There are two planes hangered at my field with Rotax 582 engines which
are both having the same problem. Each engine has about 30 to 40 hours
on them and suffer from surging and/or power failure during climb-out or
shortly after. Typically, the RPMs will drop from 6000 to around 4800
after about 2 to 5 minutes after take off. The EGTs on both cylinders
remain stable at 1100F during the power loss, but one engine does show a
marked increase in the CHT on one of the cylinders (300+).

The fuel system on both planes has been replaced twice now. The carbs
were disassembled and inspected with no indication of any blockage or
defect. The jugs were pulled on one of the engines with no indication of
seizure or carbon fouling of the rings or pistons. The plugs look
normal. Switching from one mag to the other has little effect during the
power loss.

I'm pretty much out of ideas what could be causing this problem. The
only other thing I can think of is that maybe a crank bearing is failing
and dragging the engine down as a result. But splitting the engine case
is a pain in the butt so I wanted to exhaust the simpler causes first.

Any suggestions out there?