Dear Jean-PhilippeSomething must be done to align start and end of the audio buffer for the first recording (!) and it must be done by the machine, as a human can only do this accidentally. For overdubs short volume envelope should suffice. I would say Roland's idea is ok, but the implementation not as the cross-fading incorrectly affects overdubs.
Dear Rick, Thank you for this very valuable advice, I noticed this to in the past. It did not happen this time, I do have the last firmware available for the Boss RC505, so this is clearly a design flaw, which started with the 3/30/300 series. I think Roland ingeniers thought they had a good idea applying automatic crosfade at loop boundaries, and, well, they were wrong. Best, JPR(...)