Hi Andy!
There is no model DI-120 from Behringer, at least not that I know of or that I would have found on their webpage.
If you're talking about the DI-100 (silver BSS style) I can't report the same problems you've experienced.
In case you were working with the DI-20 (2ch version), thanks for the warning. I only attempted to work with those once, and out of 3 brand new ones, two were not working with phantom power - thus, back to the old passive ones I had in my suitcase.
Apparently this really is a piece of equipment to stay away from!
Cheers, Thomas