Strange (to me) AC issue (compressor venting)

My 2008 with the 5.7L is acting very strange to me. When the AC is running, sometimes, it will vent at the high pressure bypass on the compressor. It only seems to do this when the ambient temps are above 90 or so. Below that the AC seems to work pretty well and blow cold. I replaced the compressor last year because of this issue, and the compressor was making a lot of racket, and all seemed well enough for a while. I only changed the compressor, nothing else. Pulled the vacuum overnight and filled the next day to the pressures per the r134a charts.

So as this happens intermittently, and seems to be caused by rising pressure from ambient temps I am left thinking about it being a couple of possibilities.
1. The pressure switch is failing to cut off the compressor at high pressures.
2. The expansion valve is sticking causing the pressures to spike and the compressor to vent. However, this leads me back to #1 as I need to turn off the AC inside or it will keep venting over and over.

Anyway, as you can tell, I'm not a professional, but I am trying to learn. I figure I can learn well enough for about what it would cost me to take it somewhere, and then I'll be ahead of the game next time.

 

Did you add the proper amount of compressor oil? Usually they ship with no oil