I've used longer .050 caps- up to 30' on cascades. I wonder if the unit isn't going into a sort of pump-down. What are your equalization times like? Have you tried adjusting the charge or derating(blocking ) condenser temporarily to see if suction pressure increase will change anything? Maybe add 1/2 to 1 oz? Which poe is it, 32,68,100? Who is manufacturer of comp? Is the compressor part of an OEM condensing unit or added to the prototype as separate compnent?
here is a site with some specs for POE- really only one has flow point below -40°