Hmm where did I do wrong here. I even flashed dp1 from flash.android.com site, that would definitely guarantee perfect flash.
I assume you did a full clean flash, letting it wipe user data and everything?
If so, it could be an issue with the Pixel Buds 2. I don't have personal experience with those ear buds but I recall reading that they had bluetooth disconnect issues previously.
I'd suggest trying a different set of bluetooth headphones.