I've got a few of these (27A 12V battery version) working very well with a Sonoff Bridge running Tasmota firmware.
One stopped working (but the light still lit), so after mashing the button multiple times wondering what was going on, I came up and looked at the OpenHAB logs, which showed a completely different RF code.
I thought it could have either been a neighbors RF device, OR it was an alternate code coming from the T433 86 button.
I raced back down to the unit and pulled it off the wall, then pressed the button while watching the logs. Nothing.
After that I replaced the battery and it worked perfectly again with the original RF code.
My question is, do these units send an alternate code when the battery is close to dying? I've kept the code and scripted an alert if it happens again and will report back here if it works next time a battery dies.
So I'll answer my own question. It does! There is an alternate RF code for flat battery. Just had it happen again, so confirmed.
Just to add to this, I didn't have to press the button for it to send the flat battery RF code, it just does it on it's own, when detected.