Here's what I would do in this situation.
Close the browser window for the WebUI.
Cycle power on the B2 (turn it off, wait 30 seconds, turn it on again).
Go to the B2's front panel and select the Playlist menu.
Select Play Playlist, and scroll through the possible selections.
Do you see double entries there? If not, it could well be a problem with the browser and its cache.
If you do see double entries, then there is a problem that we might be able to fix.
Before I spend a lot of time typing ;o) please let me know if there's still a problem.