What seems to be happening is, on your second camera, it is intermittently over exposing by quite a bit. That has nothing to do with your darkroom skills or chemicals/processing. I had similar issue with my old Olympus OM-10. Either metering is flaky, shutter speed is unstable, or aperture is sticking/not stopping down. But, it has NOTHING to do with your processing of film. If it was uneven development, you'll be noticing problems in frames. Instead, you have perfect frame right next to bad ones. That's a sure sign the exposure is intermittently bad.
This is your 9th roll and you solved that many problems? Seems you are too close to perfection to quit.
I've been struggling with my medium format gear and I've spent more than dozen rolls!
Tell you what.... that early in your learning process, using multiple equipment will confuse you. Stick with a camera that works. Process film ONE AT A TIME.