APU and AC trouble

I cant see any frosting but you have a restriction if it's running a low side vacuum.As said below you cant check the dryer,you just replace it.It appears that its soldered on so a bit more work to change but that's what I would do.
Unfortunately if the guts of the drier have come apart and spread into the capillary line then you may need a new evaporator assembly.This problem used to occur in some ford passenger vehicles and you pretty much had to change every component to fix it.Hopefully that's not the case and it's just the drier. Good luck