Daikin FBQ71 / RZQ71 poor cooling

[APICATS]

Thanks Brian_UK and Frank for your feedbacks.

Well noted Brian, the one inch hole in the indoor unit is for water drain checking. Thank you also for the service manual.

In answer to Frank's question: the double fans of the indoor unit (FBQ71B8V3B) are flowing air through the ducts with a duct damper controlled by a thermostat in each room (other than in the corridor); there is no fan coil dedicated to each room. Could there be another issue ?

I understand from Brian's answer 1 that refrigerant does not necessarily decay over years, therefore I would appreciate some other support to test if the heat pump works properly before seeking external assistance, for instance through reading a few codes in the 40-50 range. Some measures: currently, outside temp is around 15 celsius, the heat pump works well with 21 celsius as target on the BRC1D52, I read 21 in the remote controller sensor (code 41-0), 17 at the return thermistor (code 41-1), 19 in the exchanger (code 41-2). For info I changed code 50-4 to 01 instead of 00 to use the controller sensor instead of the return air sensor.
Last winter at lower outside temp, the unit did deliver the required heat and the exchanger temp was much higher than 19; the problem is/was cooling during summer and therefore I suspect a defect that could lower the efficiency of the system hence draining more power than it should.

Another request: If someone could send me the table of the daikin code up to 50 or more if applicable it would be much appreciated as so far I did my own recap from tips collected on various forums.

Thanks ahead for your advice.
Apicats