I have a Boss FS-6 with Maschine Plus.
I have the sampler set to Detect. I can push the pedal to trigger start and it works. At the end of the loop, when I push the pedal to stop, it does end the loop but the first bit of audio is not there. When it loops back around it starts at the correct place with the first bit of audio playing. When pushing the stop button on the Maschine in the Sampler; the loop is ended and starts playing right at the start of the loop without cutting out the first note.