A new one today... alternating squeaking and farting sounds from both pedals. I thought maybe the rubber sidewalls of my hiking shoes were rubbing against the crank arms, so I moved my feet out a bit. Nope, still squeaking/farting.

So I checked the soft nylon platform pedals. Nope, both seemed okay.

Turns out both shoe soles began separating identically, both with identical holes in the separated soles, both forming identical bubbles that compressed with a squeaky fart sound when I mashed down, then drew in air for another go on the upstroke.