Automotive Air Conditioning Information Forum

I have a 2014 Chevrolet Silverado 1500 lt 4wd. I've always had issues with the AC. I thought it was due to a factory issue I kept hearing about with a ground under the dashboard ( may still be a separate problem). Anyway, this year the AC was working okay but then stopped blowing cold air. I checked the freon level and it was low. I added freon and it worked great for about 2-3 weeks and then nothing but hot air blowing. I crawled under the truck and saw a lot of oily residue/buildup on the AC lines directly behind the bottom of the radiator. I've seen no oily stains in ir on the radiator area. I added freon and sprayed soapy water on those lines and found no leaks. I sprayed soapy water on the block where the lines go through the firewall and instantly had rapid bubbles but from behind the lines where the gasket is between the block and the firewall. Could this just be cabin pressure? I had all four windows down and had the AC on high and recirc. I've attached a screenshot from a short video.