Mitsubishi City Multi

[The Viking]

OK,
As you verified the refrigerant charge, the most likely cause of the system not ramping up/delivering 100% is that the controls is not seeing what is going on in the system correctly.
One or more of the pressure transducers or temperature thermistors will either be out of calibration or not in the correct place.
It is possible to find this without the laptop interface, it just takes slightly longer.
The best you can do is to follow the service manual and go through all temperature and pressure readings one at a time and compare the values with what you measure the actual temperatures/pressures to be.
One degree or two, or 1/2 a bar on pressures, will probably be OK and not affect the running of the system but if you find a reading that is 5-10 degrees, or even more, out then you probably have found the cause of your issues.

(A "cheat" is to check all the temperature sensors after the system been off for a while, say overnight, as most temperatures in the outdoor unit, apart from measurements affected by CC heater, will be that of the ambient temperature. This makes it easy to spot any readings that stands out)

Also be aware that when thermistors fail they might show the correct temperature / resistance from time to time but go out of calibration if they get wet/get moisture inside, making them harder to spot.

Another thing to look out for is running currents, a loose connection or poor power supplies might increase the running current and this might also limit the compressor speed.