Just seeing if anybody here can give me any advice on this issue.

I have a problem with a coldroom. It's quite small, only 3m x 3m. It's a pump down system and the condenser is located about 25 metres above the evaporator. I have worked on quite a few coldrooms but none which have an oil separator on the condenser and also the compressor is a semi hermetic Frascold compressor, I'm used to working on fully hermetic.

Basically I was called out a few days ago and found the system tripped on LP. Found that no gas was getting through the TEV. Checked the orofus and it looked clear so presumed the TEV was at fault. Replaced TEV and orofus, system worked fine for 2 days then off again. The restriction once again is at the TEV. On inspection there is oil inside the TEV so I'm guessing this is what Is causing the valve to block up? The ambient temperature for the last week has been about -5 so not sure if this is a factor. The Tev is external equalising. Also the compressor oil sight glass is full. I'm back at the job tomorrow so any advice or pointers on what to check will be a massive help.
Thank you