Unstable program change to A4 - MD

Hi, had the OT as master to A4 and MD using the autochannel for a year or so
Everything worked fine, when i change bank/pattern on the OT, the A4 and MD do the same

However this week, just a week before my next concert
It suddenly becomes unstable, sometimes when i change the pattern on the OT the A4/MD stay on the same pattern

Checked all the options, and midi channels, conflicting data etc, nothings changed, checked the midi cables, seem fine
and of course the 3 machines are set to the same pattern length

I found if i reset the OT then everything goes back to normal
but a bit worrying,especially with upcoming gigs!

anyone else experienced this
any advice???

cheers