Keano66
Success!. Ok what you need to do is to go into MIDI - Playback and recording- Turn off 'Always Echo Current Midi track'
Thanks for the responses so far - hope this helps other people who have this problem.
Whenever I select a midi track the input echo button turns on for that track. If it doesn't I can't hear the midi synth. If I understand you correctly using your workaround, I'd need to manually turn on input echo for each midi track I wanted to record.
If so I'd rather use my workaround which is when it gets stuck, just hit the global input echo button in the Mix Module to turn off all input echo buttons. I hope this is fixed in 2017.02 so we can quit using workarounds.