There is no interconnection in the tanks piping systems, so it must be at the tank level.

My guess is that the spray bar in some manner is mis aimed, or has too many outlets plugged with cruddies, so that the pump is squirting liquid out where the piping joins the spray bar.

The public darkroom comment makes me suspect that the machine needs a good cleaning, roller scrub, and spring and spray bar inspection. I had good sucess cleaning the spray arm with a longe scrubby thing marketted at claning glass baby bottles

A transfer rack clean off also would help.

Maybe the overflow of the developer tank is somehow plugged, and the overflow of tank 1 is being washed into the next tank, or event the third tank along the end areas if the machine is not mounted on a levellled surface?.

I find myself curious how they run theirs. The first tank is usually deevloper, because it has the most accurate thermostat ( or at least mine did until it went flaky.)

The last tank I thought would be blix, with a water bath of stop between them. Maybe they run tank 2 as blix.