I've had 2 different medium temp R22 rooms in the last year or so that were running with POE from new that shared the same problem.
They were both LP pumpdown systems.
After cycling off, they would come back up to temp and the LLSV would be energised then the compressor would start short cycling.
The first time I came across it, I checked the pressure at the suction service valve and found it pulling straight down to 20 odd PSI, cutting out opn LP then going straight back up to 65 and repeating.
I put a gauge on an access fitting on the suction header on one of the blowers and found it sitting at somewhere around 90 PSI.
The suction line leaving the blower was trapped, followed by about a 1 meter riser. The riser was frosted for the first few inches then returned to ambient.
My first thought was an oil lock in the trap, well, not my first thought, but the first one relivent to the discussion as the other lones of investigation didn't pan out.
Long story short, I managed to pump down the evap and drilled a hole in the bottom of the trap, expecting to get a heap of oil out of it.
I would have been lucky to get a table spoon full out of it.
The above investigation took place over a couple of months on and off.
At one point I even suspected that a piece of rag might have been left in the pipe somehow during the initial installation and opened the suction line at the top of the riser and blew it through wit a heap of nitro. to no affect.
What it appears to have been was the POE oil frothing up in the trap to the extent that it blocked off the flow of refrigerant from the blower.
This wasn't a conclusion that I came to lightly, trust me.
At the beginning of this year I bit the bullet, pulled the scroll out, poured out the POE oil and replaced it with 3GS. The problem hasn't recurred since.
I had similar problems with another R22 system in a different store later and rectified it in the same way.
Has anyone else seen this?