lg split unit

[karabelarid0]

hey guys i have another question
i went to a call for one of those lg ductless units and put my gauges on after the unit was on and pressures were like 10psi on both sides. turn the unit off pressures came up to 225psi and it's r410
so when the unit kicks in it pumps the refrigerant in to the compressor pressures drops to 10 psig. checked service valves they are fine took all the refrigerant out and first ran nitrogen thru the line set to see if there was anything blocking it but clear. did the same thing for the condenser unit and it seem to be fine too so i vacuum and start putting the refrigerant back in. put in around 62oz what it said on the rating plate and pressures was 150 on suction and around 180 on discharge. even tho i tried adding more refigerant i cant get the discharge pressure higher. only the auction goes higher. i'm starting to think it might be the compressor. what do you guys think? how can i make sure it's the compressor?