"Max UDID reached", Windows Beta

I have installed the Docker beta on (1) a Windows VM; (2) an old Acer laptop; and (3) a new Surface Pro. Sharing volumes fails on (1) and (2), but works on (3). Unfortunately, (3) isn’t a development-capable machine. Happily, I was able to trade up to a Windows Surface Book, which should be. Unhappily, the new machine is the one on which I receive the Max UDID message.

I have not shared my token, just tried to find a machine on which sharing volumes actually works. Is there a way to reset my UDID count, or to decrement it? I still have access to machines (1) and (2), but not (3). Failing that, can I request a new token?