Hi
This is a split unit,cassette and going thru intermittent trip with error code E57, which indicates shortage of refrigerant or closed service valve. Can someone please point out where my problem is.
I have replaced the the PCB with all thermistors in the indoor unit, have recovered system gas(R410) and recharged unit thru designed recommended weight, but unit is still tripping intermittently with E57 error code on wired remote controller.

Stressing out on this one, and therefore any assistance will be greatly appreciated.