It's not uncommon for a unit not to pump down all the way & it doesn't mean there is anything wrong with the compressor especially if there is a long line set involved. Either way I've found the fastest thing to do in that situation is just take the recovery can, hook it up to the high side while the unit is running normally & let it pump a few lbs. into the can. After you lighten the freon load a little it usually pumps into a vacuum real quick. You don't even have to bother hooking up the recovery unit. I've done it hundreds of times with rarely a problem.
I like this idea a lot. This and getting a heat gun for what should
have been to me obvious icing.