At least on the FR935 (fw 6.0), if you have an app/widget that opens the Asset Tracker Ant+ channel, it doesn't release that connection until you turn off the Garmin Astro/Alpha dog tracker. So if you swipe through the Garmin Dog Tracker widget and then start an app that wants to open the Asset Tracker Ant Channel, it won't find it. Similarly, if I've run my dog tracker app, the Garmin Dog Tracker widget won't be able to connect after I close my app.
As soon as I turn off the Garmin Alpha, I get a message on the watch that the "Asset Tracker as been disconnected". I can then turn the Alpha back on and it is imediately visible to other apps/widget.
Note that since it is just Ant+ connection, I can have any number of watches/devices connected to the Alpha. It's just the connection on the single device that is having the issue.
Is this a bug or is this a "feature"? Might be just an issue with the 935 on the latest FW. I don't think I had this issue a few months ago but can't be sure. Maybe this is a side effect of more multi-tasking features on the watch.