When selecting points with a lasso, selected_points() saves the correct date, but sets time to midnight local time for every point. (Displayed as 05:00:00Z in reactable table.)
Probable trigger - occurs if any of the selected points in range have time set to 00:00:00.
("Selecting 10+ points" hypothesis debunked, able to selected 28 points as long as none of them are at midnight.)