I've had plenty of spots show up on the sensors of the GX85 and A7ii.
However, they are usually quickly dispatched with the sensor-pen and a
blast of air. The Canon 6D was a living nightmare compared to these,
though. The 6D was like constantly doing battle with diaper rash.
My experience with the various Four-Thirds cameras is that the E-1 had
the best sensor cleaning or dirt mitigation system of all. The E-3 is
also really good once I removed the years buildup of haze on the
sensor. Something I also had to do with the E-1 and L1 at some point.
I've had no-shows on the E-400. The E-300 hasn't revealed any yet, but
I'm rarely using it. The L1 has been quite well-behaved, but I've had
a couple occasions that have required brute-force cleanage. But
overall, I'd say that I'm disappointed with the GX85 in sensor
cleanliness. It's not as bad as a homeless camp, but it's certainly
not up to par with the cat-like self-cleaning I'm used to in the E-1.
For both the GX85 and A7ii, the fact the sensor is always exposed
instead of hidden behind the shutter is likely the biggest culprit.
I'm constantly changing lenses and using legacy OM glass, so there is
a lot of air pumping in and out of the camera and the sensors ain't
For those keeping score in the OM List Drinking Game:
Themed Olympus Photo Exhibition: http://www.tope.nl/