I was experimenting with different configurations between the microbrute and the volca beats.
All of a sudden, the sequencer stopped responding to key on or Hold mode. The only way to trigger the sequence is to use the Tap Tempo button, which cycles through each step in turn.
Tried reboot, reflash, standalone, connected - whatever, the result remains the same :/
Erm.. help?!OK - you can all stop worrying
It was the Sync set to Ext. I had assumed that this would only affect the response to MIDI clock.