I think there is a problem that can occur with the BT-ARC1A (and other similar devices, it seems) with LXQt components in Debian Buster (fixed in Bullseye or with up-to-date pavucontrol-qt.)
Right now I can neither upgrade to Bullseye, upgrade my pavucontrol-qt, or download and install Plugable’s PlugDebug, because of other time commitments, but I will update this thread when one of those actions solves (or does not solve) this problem.
Welcome to the Plugable forums! It does seem that there are issues presumably with our BT-ARC1A and any devices that use the same Bluetooth profiles like A2DP and other related multimedia profiles with Linux.
As a suggestion we do have a knowledge base article with instructions that tend to fix Bluetooth audio problems on Debian-based distros distributed after Ubuntu 16.10.