When you press the button on the S-A-S, does the light blink? If not, it might be a bad contact under the button, or a weak battery.
If the light responded just fine, then it might be an issue due to the poor transmit range, coupled with the poor RF reception range of the CM15A. In that case, a different remote, a CM15A antenna mod, a S-A-S reflector antenna, or maybe even repositioning the S-A-S might help.
Did you test to make sure the battery was still good? The weak battery might have been causing it to reset to housecode A.
It could have also been caused by bent or dirty battery contacts.
I should have been more detailed. With two separate units, the red light blinks fine. Although it takes two or more presses, they will eventually work, so I know the codes are still retained. I have also changed batteries. We're also talking RR501 and V572 receivers, no CM15A.
It's almost ... as if ... the oscillator does not instantly come up right on frequency. There’s no heating going on here, so it’s not like it’s temperature drift.
Here are some high tech questions: If one holds the button, the LED continues to flash. Does the command get transmitted each flash? Or multiple times as the button is held? Is it AM or FM modulation? If the command gets transmitted only once, and the continuous LED flash is just for operator fuzzies, then perhaps the oscillator start-up and subsequent command encoding occurs before things are really stabilized, and the command (to the receiver) gets corrupted. Maybe that’s why a subsequent press most times works. If the command repeats, then you’d think the subsequent commands would be stable.