Tape a clear plastic bag around the end of the copper pipe, to make sure that the drip you have seen is from the inside of the pipe and not running down the outside from frost/dew/condensation.
It also looks like the elbow on your condense drain (white pipe) is split and the drip you are seeing is quite likely to be from that - based on your report that the pressure is holding at 1.5 bar!
Also... condense pipe should go into 32mm waste as it exits the wall... currently looks at risk of freezing during winter, which might explain the split!
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