Ford Escape 2009: A/C Repair Question

Last year I was my compressor has failed, and I got it changed. The guy at the shop told me there was a leak in my low pressure side? Or was it the high. It was the smaller of the two pipes, but he then insisted it was fine. This year around May I lost all my freon, and the car a/c was blowing hot. I went, they just filled up the freon. I went back again last week, and the guy said it was the pipe. Got the pipe replaced, and now a/c blew cold ish air for 2 days. then went completely hot, but compressor runs. Went back, idk what they did but after 5 minutes the a/c line was cold and I had cold air. They said my compressor was going bad again thats why i didn't have cold air. but wtf? The a/c works fine currently, but I know the problem will come back.

NOW I notice this new sound. When the a/c is at max, there is no problem.
however, when the a/c isn't maxed out there is cold air for about 5 minutes, then this PSHH sound gas escaping? Or pressure release sound, and the compressor stops for 5-10 seconds, and warm air blows. Then it goes back to normal. I was wondering what might this be? Accumulator? Expansion valve? Or is it the sensor? Also, if there are any part #'s given that would be nice too, as I like buying my own parts. Thanks.