On Dartmouth there is a set of 2500+ object records in a set called "Civic Collection 2". In the Batch Editor I am applying a "related collection" - the Civic Collection.
The batch editor runs successfully but the object x collection relationships are not applied.
The batch mode drop-downs were being hidden by the metadata info panel button due to stylesheet issue. The batch editor works fine so long as you select a mode, which I'm guessing you weren't doing because you couldn't see the drop-down.
I just ran a batch and it worked.
Nice! Yeah the drop-downs were not showing. Didnt think of that cause I was seeing the relationship type drop-down. It's working now though.