I don't know of anyone else having so much trouble with their particular garage opener brand/model as you have
But IMHO on this particular issue, I would consider it a slight benefit (added security perhaps?
).
Anyway it makes no sense but maybe others have extra input on this.
First the frequencies are different, then the fact that the Moteino RFM module is in receive mode all the time (except when it transmits a status change or an ACK), so I don't see where is any RF interference between the 2.
I suppose I could try to lengthen the GarageMote wires and move it further away. The GarageMote reads -72db at the Pi Gateway. so I suppose I could reduce the transmit power on the GarageMote.
At the very least use RFM69_ATC which should automatically dial down TRANSMIT power only, this is a good practice on any transmitting mote - only transmit as "loud" as necessary, "louder" is pointless and a waste of power especially on battery powered nodes.
If you can try a longer cable ... it won't hurt to see the effect. I would probably try the same thing myself. I wonder if any other EMI interaction or the proximity of the magnets has anything to do with this...
How about this...I recall you had lots of issues with the actual connections to the opener itself.
Try disconnecting power to the GarageMote but do not disconnect it from the opener. Then see if the range issues persist, if YES then something is wrong with the opener and it just won't like anything else connected to the terminal intended for the wall-attached opener button.