I fear my EOS-3 is dying

Recently I have been tweaking my one shot E6 process with new chemicals. I use my EOS-3 for these kinds of things because exposures have been consistent and proper. First roll I did went fine, so I started my process of tweaking dilution and time to maximize mixing for one shot. Things started to go sideways pretty quick, I got one roll that was so dark it was unusable, so I backed off a little bit on the process. Next roll was dark with one or two frames that were OK. This was done indoors with a flash and the flash verified a proper exposure. So I decided to do some outdoor shots without the flash. Same kind of results, mostly really underexposed shots with one or two properly exposed shots. All the shots were with similar lighting, no heavy backlight or shadows, all pretty even.

I'm going to stop the E6 tweaking and put a few rolls of B&W through it to verify, also try with a different lens in case it is a lens acting up. Really hope my EOS-3 is not dying.

Before you put a roll of film through, try testing the camera without film to make sure that:
- it's metering the scene correctly (compare to another light meter, sunny 16, or a light meter app),
- it's reading the DX code or ISO is set correctly,
- it's firing at the correct shutter speeds,
- it's opening the aperture fully for viewing/metering, and stopping down the aperture correctly during the shot,
- the mirror and shutter are opening fully.

If any of these things are off, then you'll have problems. Continuing to put more film through the camera before verifying correct operation will not shed more light on the problem.

Ya, I did those things when I first got suspicious. If the results would have been consistent and wrong that is one thing, but a few random good exposures mixed in is odd. I have had this camera since it was new in 1999.

I did run a roll of B&W through it and it seemed OK. I used three different lenses during the test and all exposures seem the same.

So now I need to ponder the E6 process, maybe I contaminated one of bottles, but doesn't explain the random frames on the same roll. In 30+ years of doing E6, don't think I've seen this.