Now that is interesting, moving to 7.2 and the MIO+ won't recover from standby and tune DVB-S2X on tuner A, and this is similar/ same as VIX 6.3 from what I can tell.
ATV 6.3 was more predictable and even if the USB HDD was in standby on 6.3 it would continue on tuner A.
ATV 7.2 log attached.
[Edit] Actually it is so brittle that If I edit Tuner A and don't zap back to the service, we are off tune/ 0 signal.