I'm seeing this thread too late to make a difference, but will point it out anyway.
Another thing to check when there's corrosion is that the threaded inserts in the seal plate are still solid. That aluminum+water reaction does something to the plastic. I had a Pentaire pump (older Whisperflow, but it has the same arrangement) where most of the inserts spun when I loosened the bolts. One broke out completely. Had to replace the plate. Others were just wiggling. I was not applying much torque.
In the photos it looks like yours are basically okay, but next time you have the pump open, give a check.
Good luck with it!