In FMP9, I often displayed fields formatted as checkboxes in what is perhaps an unusual way. Specifically, I resized the field to be square-shaped, hiding any label of the checkbox. (In fact, I used a value list with only a single value.) I labelled the checkbox seperately, to the left rather than the right, with ordinary text. In field control/borders, I set the border width to 0pt (leaving all borders turned off, as default). This turned the entire field into a checkbox, instead of having it function as a field within which was a smaller box that could be checked. If checked, the field would fill with a large X, extending to each corner of the field. All of this was done purely for aesthetic reasons, it looked better than the default behaviour (to me).
After converting databases with such checkboxes to FMP12, there are serious problems. The field no longer shows an X, appearing blank for all records regardless of whether it was checked in 9. Also, clicking on the field does not check the box, or change the value stored in the field.
Unless anyone has a better idea, I suppose I'll change all such fields to ordinary text fields and then make them buttons, attaching scripts to check/uncheck the boxes by entering/removing an (alpha) X into/from the field.
I just thought I'd post a warning about this bug great new feature in case anyone else does checkboxes the way I do and didn't yet notice they're all broken now.