[forge:site-support:#6861]
I accidentally entered "13:00'" (mistakenly adding an apostrophe) as a start time in the availability dialog then clicked "Save", there was no new event added, but all my existing timeslots were changed to the values just entered (day, start, end). When I entered a valid time and saved, all the existing slots reverted to previous setting. I was able to reproduce the behavior (see screenshot).
Confirmed, if any bad input is entered (eg., just pounding the keyboard), all existing timeslots will just show the bad input data entered (including day of week). This appears to just be a display error though, reloading the "add availability" page will still load the correct data.