Im newish to the trade so be easy on me.

Found a Toshiba DX unit short of refrigerant (R410a), electronic sniffer going off at flare.
Gauges showing 70psi suction and 290psi Discharge.

I was lead to believe that when a unit is short, the refrigerant bubbles off early causing to much superheat. so frosting early in the evap coil and expansion line, and a warm suction pipe and hot discharge pipe.

But this dx unit had a sweating expansion line and a frosting suction line through the suction line accumulator and all the way back to the compressor. Airflow was good over the evap coil.

Just wondered why this is happening. Sorry for the noob question, im still learning.