[mythtv-users] Using On Air Guide and Schedules Direct on the same lineup.

[Clay]

Still sorting out tuner inconsistency with my A180 and ATSC115.
Same box. Same lineup. Same cable, split just before entering the cards. I've switched them to rule out one or the other being bad.
Both cards /should/ use the same frequencies and multiplex yet one card can tune channels the other can't. It changes with time of the month, phases of the moon, etc. This week, the A180 is only getting a few channels while the ATSC115 is getting all the channels in the source.
Been looking for anything that would cause one tuner to get all the channels and the other only some.
Poking around Channel Recording Priorities, I see that some of the channels have "Use on air guide" checked along with (presumably) getting channel info from Schedules Direct.
Could this hose things so the tuners get channels one day but not the next?
Any other ideas? 
tia.