My friend J has an MC6 and he asked me this question that I couldn’t solve. I’m assuming he’s running the new 3.9 beta firmware since this is a new feature only available on 3.9 and his MC6 is new.
When he says “exposed tap” he’s talking about:
“%BP” Placeholder in Preset Short/Toggle name to display the current MIDI Clock BPM.
Here is his problem/question…
“So I’ve set my midi clock with exposed tap when pressed (so I can see the BPM on the mc6). When I tap, it changes the tempo as it should everything is fine. When I press it again to try and tap a new tempo, the tap is LOCKED and the tap no longer functions. Only a reboot brings it back. HELP ME!!! 
”