My motor screech sound was intermittent at first and came from one tank's pump going dry. It turned out that one chem causes the tubing to swell in my machine.
I converted my machine's tank sequence from dev blix wash to prewet, dev, blix, and then wash in the separate w/d unit. Mostly because the digital thermostat in my bath 1 was kaput.
I found that the RA4 developer, either on it's own, or though some interaction with past chem residues deep in the hoses, causes the hoses for that tank to swell.
Inside the machine the hose had swelled to the point of kinking and pinching off flow in a short section.
The solution was a simple shortening of the pipe in question. Getting the machine apart to affect that fix was the usualy PIA that any fix on a CP-3x machine is.