Mitsubishi electric wall mount under performing

[Ben23]

I have just looked at a callout for a mitsi electric split for a comms room it had compressor and boards changed last year. The air off temp when set to 19 c is only 14 closest to pipes going in other side of coil is 21c air off!

Im awaiting my mate to drop my gauges he borrowed but is this more likely an expansion valve issue than a low gas issue as youd like to think it would be correctly charged as its been worked on recently.
One pipe is frosting in condenser as seen in photo its a pipe coming out/to liwuid reciever