yes it is...but just throwing an idea out. Maybe due to satellite wobble the signal on 127W is closer than normal
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That sounded like a reasonable idea, ie maybe 125 and 127 were drifting close together, and were closest at night. So I made a table of the positions of 123,125, and 127, using the latest keps.
http://www.eskerridge.com/BJ/sat/amc21drift3.htm
It turns out, however, that 125 and 127 are further apart than normal, and with the daily orbital fluxuations, the times I saw the problems are when they were furthest apart. So it doesn't seem to be that they are too close. It's possible that somehow side-lobes are involved, and when they are further apart, the sidelobes come into play. I ran into side-lobe problems with sats that were 2 or 3 slots separated, ie either 4 or 6 degrees apart, (ie I could lock transponders on sats 2 slots away while still locking transponders on the sat I was aimed at) but that was with a different dish, so this one might have sidelobes closer.