Mitsubishi electric wall mount under performing

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

Could be expansion valve or SoG. Never assume anything with a repair.

Order the complete expansion valve and head, then try the new head first. If that does not work, you will need to reclaim the gas and the weight will indicate if it is short.
If it is not, then change the valve body for good measure, leak and pressure test and get it back up and running.