Sound output automatically changing from bluetooth headphones to internal speakers

OK, I am getting this same issue again. See below:

As the above screenshot should show is that my BT head phone is actually active, but it isn't being accepted as the active output device even though I've selected it in Systems Preferences -> Sound. If I disconnect the BT head phone from BT and reconnect then it does become active. Is this related to other reports I've seen of BT and WiFI issues?

I've accidentally found a solution to this issue. At least for me....

I downloaded and installed https://mac.softpedia.com/get/Audio/Background-Music.shtml.

I get the following on my menu when I run this app ...

And when I check the Audio control menu I now see

By selecting this second Sound Blaster Jam Input, this then remains active constantly. No more dropping of the BT connection.

What version of Catalina are you running? I have 10.15 (19A602). I experienced the same issue that you report, but then upgraded to this version of Catalina and I've not had this issue recur. So, I don't know if it's that upgrade, or a coincidence?