BitPerfect 3.2.0
Sorry my fault, I should have said I was already using Bit Perfect (3.2.0). As I had tried with and without and it made no difference to the crackling, I had eliminated that as being the cause of the problem. Luckily the crackling does not seem to have reappeared on either MBP or Mac Mini. As the effective change was stopping and restarting Core Audio, I think that is where the problem must have been. I tend to play FLAC files through IINA or iSkysoft Media Converter/player Pro but if I have been sent FLAC files I usually convert them to ALAC at the same bit rate.
BitPerfect 3.2.0