MSD Garage door tango??

It is unlikely that the problem is at the manual switch, because it typically engages the relay coil, and that takes more current than would get there remotely by RF. If the wires to the switch are acting as antenna, for remote receiver, then the fix of capacitor by Darthomas may not work, because the signal is likely getting there common mode. The capacitor would be a differential mode fix, and at switch end is pointless. A more suitable fix could be to apply a snap-on common mode choke at garage opener, on manual switch wires.

But with that said, a fix at the garage door will not fix the problem source, the MSD, so who know what other interference and problems it may create when driven about.

MSD CDI is multi-strike at lower RPM, and the re-strike interval may get by the simple decoder strategy of the RF receiver. You could try reprogramming, the receiver and transmitter with new codes. That was done using selector switches on most older models. Again no fix at problem source.

A better fix is to perhaps use an Ohm meter to measure plug wire resistance to insure a plug wire or two has not opened up. Also check for spark leaks on a humid day at night, carefully looking at all HV boots and cap terminals. Check distributor cap, rotor, coil to cap cable .....