Thanks for your feedback guys. Another weird thing that happened when I upgraded(?) to the APAC v2.9 firmware ... it deleted some of the sensors from my watch. It's good to know that it's not just me having connectivity issues and hopefully Gamin is doing something about it. In the end I did a full reset on my watch (and lost all my data :( ) and then, and only then, could I get my recalcitrant sensors to connect to the watch via ANT+.
I have seen the same issue and the way I've solved it without full reset (and therefore keeping all my settings and data) is to:
1- delete the device from Garmin Connect Mobile
2- Turn off Bluetooth on the watch
3- Power cycle the watch
4- Delete all the ANT sensors from the watch
5- Reconnect all the ANT sensors.
6- Reassociate the watch to Garmin Connect Mobile.
It's tedious but not as much as recreating everything from scratch and rebuilding your VO2max history.
Hope this helps.