I was multi-selecting some files in v2.23s today with gaps (I wouldn't have had to if the track sorting routine made a distinction between blanks and zeros. They are definitely not equivalent!) and found that sometimes my fields went to a single tag without losing the multiselect and at other times behaved normally. The fields go to a single tag of the last item selected upon selecting in the track field and the multi-select remains. I thought I would report it since you have been working on some routines in the grid.
P.S. I should add that the behavior occurs only when the last select opens a field in the grid. That seems to occur with a slow double-click. In any case opening a field in the grid seems to be incompatible with a multi-select. The solution as I see is it that a click should not be able to open a field if the shift or CTRL key is down.