Hi,
I have exactly the same problem with my OP7 (GM1900, OOS 10.0.10.GM57BA). I had OP Bullets Wireless 2 and bought as you the Z version, same problem : during calls (and only during calls), my BT connection drops randomly (sometimes no problem, and some other times it could be after 3 min of call, then reconnect, then drops after 8 min, then reconnect, then drops again 2 min later, and can reconnect...or not). Really random issue, but it occurs often.
I tried today these operations (
https://forums.oneplus.com/threads/bluetooth-connectivity-issues.1358120/#post-22472678), currently testing it. I had a 23 min call without bug after these operations.
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