I've been using the whitelist and haven't seen an issue like this (neither complete failure to reconnect or changed Bluetooth address), but I do choose to pair when connecting the watch in Gadgetbridge. Maybe you could try that?
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I've been using the whitelist and haven't seen an issue like this (neither complete failure to reconnect or changed Bluetooth address), but I do choose to pair when connecting the watch in Gadgetbridge. Maybe you could try that?