Oreo Pairing Syncing?

I have Oreo, on OnePlus 3T. It worked fine with my Vivosmart HR+ - until Garmin Connect Mobile (GCM) 4.2 came out. Since then it did not work until I went back to 4.1.11 - since then absolutely no problem. You'll see several threads on the topic, which I don't think is related to Oreo but it would be interesting to know what GCM version you are currently on.

Thanks. I've been on 4.2.2 for a while. Works fine for me on Nougat.

Hmmm, interesting! I wonder if perhaps there is an incompatibility with Oreo then. If so I would expect/hope that Garmin will fix as it's not so easy (or desirable) to roll back Android releases. Or perhaps it's only affecting some Garmin wearables?

Somehow, I think these kind of issues would be relatively device independent if the devices are running their latest firmware and past the bleeding edge. My guess is that the issue is as much with Android and/or vendor "enhancements" as Connect 4.2.2. Consider what the Huwaei people were experiencing. Most other phones were stable.

One other thing that can bite is that BT and WiFi on 2.4 Ghz share the same frequencies and can interfere with each other. I had that issue with my old phone. If I turned on BT, I'd lose my WiFi connection. If it stayed connected it would slow to a crawl. Fortunately, my Zenfone has 802.11a.

I did the update to Oreo today. Absolutely no glitches with GCM - so far. If anything, the connections are more stable with Oreo.

Me also got no problems after upgrading at all.
GC will work exactly the same, as before.
Vivoactive 3 and HTC 10

Just got my nokia 6.1 (oreo 8.1.0). I was able to pair my fenix 3hr without issus. Directly after pairing it synced fine. Until you loose the connection (out of range). After that it's unable to reconnect. Turning bluetooth off/on does not help either. Also tried the device connection aid setting in the gc. Didn't help either. The only way I seem to be able to let it sync again is by removing the watch from gc and bluetooth settings and then repairing.

Before this phone I had a moto g5 (nougat 7.0). The watch synced fine on that with the same gc version.

Same experience here. Using a Nokia 6.1 and 7 Plus (both running Oreo), connecting a Vivoactive 3 and a forerunner 35. Connects without problems and are working until the connection is lost because the phone and the watch are out of range. They will never reconnect again, besides removing the watch and reconnect.
The GC is 4.5.1 - I tried to downgrade to 4.1.11, but it didn't fix the problem and after a day or so, it was auto-upgraded to 4.5.1

Syncing is fine here using Xiaomi Mix 2S running MIUI 9.5 but having issue with music control

Just solved it within minutes, looks like Oreo just completely reworked the access control, Garmin Connect App needs smart notification access to be able to control music