Check your WiFi signal strength using Settings > Maintenance > WiFi Strength. (I got that from the Brennan website on the Menu page.)
Your signal strength should be better than -50 (-40 being better, -60 being worse) and not fluctuate wildly.
To improve your signal strength, try the following:
Move your B2 closer to your router.
Switch the WiFi dongle to USB C.
Move your WiFi dongle to the end of a USB extension cable.
You can buy a new WiFi dongle that has an antenna. Look for one that has the RT5370 chipset.If none of that helps, you could try plugging a network cable between the inside back of the B2 and your router (and remove the WiFi dongle). There is a picture showing that on the Brennan website.Small nit to pick: the Brennan units do not receive DAB radio broadcasts. DAB is broadcast over the air. The Brennan units receive internet radio, which is not strictly speaking "radio" at all, as there are no radio waves involved, but everyone calls it that anyway.