Welded high side liquid line on unit #1 with new copper coupling. Pressurized line set and indoor coil to check for leaks, this was good. Removed nitrogen charge for the standing heat pump and vacuumed system down to 500 microns. Weighed in charge to system 5.6 lbs per nameplate. Tested system and measured amp draws. System is running but the compressor is struggling, the system cannot pull in anymore charge than what I’ve added, either the motor was damaged previously by running with only nitrogen or there is a restriction somewhere in the system. Additionally added small amount of leak dye in case the system has a slow leak. Swapped out thermostat for system #3 with WiFi model Honeywell.