when using my polar h10, the watch often doesnt recognize the polar device, so i have to switch off and on the polar until the garmin connects with it. with the older firmware i never had any issues with my external hr device. bluetooth connection to smartphone seems in the other hand stable as before.
***** Update *****
Was using polar oh1, which is connected via Ant+. After Fw Update of polar device and unpair/repair and reboot watch everything seems normal again.