My restored VP, that had a brand new genuine comp, and only the 3-4th time using it, it started to make a horrible rattling moan. It only did it on hotter days, cooler days is sounded ok.
I have since fitted and modified an aftermarket one, but still haven't gone back to get it gassed, that was 2019.
The oil that came out of that NOS comp after it got really noisy is pristine, so I don't know what's wrong with it.
On my other cars, the AC works fine, but they do loose gas often via the hoses as the crimps squish out with age and you find that the cars that loose gas, you can grab the hoses and spin the rubber on the crimped fittings, often very easily. So there's your answer where the gas goes most often.
Starting with VR, they changed the hose and crimp style to what is modern still today, they very rarely have issues, it's only VP and older that have issues with hoses. When I got my restored VP's AC gassed, I had the old fittings cut off at the crimp and had those in situ type modern DIY crimps and fittings welded on to the original ones since the old part of the fittings were unique and obsolete. Very handy solution, but it took me ages finding an AC place, eventually one in Bendigo that could even do it, no place would even bother looking at making a set of hoses for me. I know the pain of these AC systems very well
Compressors were always hit and miss, those Sanden comps are overrated in my opinion.