and I think it’s all related to this bug which affects regular, non-plays free tracks:
If you change parts (with a change in a track’s default sample) and you make that change between step 16 and step 1 (on a 16/16 standard length pattern) - you get the first trig playing the old sample and all the following ones are SILENT until pattern restarts
oh boy… I just tested this again where the sample doesn’t even change. I just copied part one to part two and the first trig played (obviously same sample as expected) the rest of the pattern was SILENT until pattern restart