It took me a while to figure this out, so I though I would mention it. I have a geojson file in which the features have a property called precinct, which is a string, but the string always contains an integer.
And I have two indexes in which the documents contain a precinct. In one it is text, so I do region maps with Terms+Precinct.keyword. In the other it is an integer and I do region maps with Terms+precinct. Both sets of maps plot correctly, but for the second one I do not get any mouseovers. Clicking to add a filter works for both, it just seems to be mouseovers that are missing.