I think this may be related to a problem I mentioned here - related in that checkboxes to select options, which were previously working correctly, are now behaving erratically.
I just opened a file I created a few weeks ago when testing the then new autocomplete feature. The page includes an autocomplete dropdown with none of the three options set - however, all three checkboxes are selected. The autocomplete works as it should however. It’s just the UI which seems to be working incorrectly.
There is a detail which has changed in a way similar to the issue I mentioned in the post referred to above. Switching the options on now omits ="true" - eg from matchstart="true". Again, this may not be relevant; it may have simply been removed because it’s redundant.