Have you tried using an app like Bluetooth Classic: Bluetooth Classic APK for Android Download. You can download it from the Aurora Store. I tried a few different strategies and apps when I had trouble getting my headphones to reconnect, and this app helped perfectly.
Edited 9/11 (I previosuly linked to the app on APKPure’s website and after someone complained about APKPure, I am replacing that with a link to the original app in Google Store).