Both high and low side pressure needs to be check at the same time well the compressor is running.
Pressure readings well the compressor is off mean nothing.
I payed next to nothing for it, knowing that it had issues so I don't mind investing some money to get it fixed.
Unless you have refrigerant, scale or charging cylinder, vacuum pump, brazing equipment, a set of refrigeration gauges, leak detector, etc... and the skills to use the equipment you would need to call some experienced in sealed system repairs.
Could be some kind of restriction or low on refrigerant. If it's a restriction you are probably looking at some kind of problem with the dryer or cap tube. If it's low on refrigerant the sealed system has a leak. The leak would have to be found and repaired. During any kind of sealed system repair the dryer should also be replaced.
IMHO if you have the equipment, skills and the experience to do this type of repair yourself it maybe worth trying, if not forget about it and spend the money on a different refrigerator.
Just my 2 cents...