I discovered a bug when using a date filter with a 'between' operator on APEX 20.2 and also managed to reproduce it on apex.oracle.com (APEX 21.1) in the Sample IG app on page 3 (see GIF below).
After adding a filter on a date column with the 'between' operator and reopening the filter by clicking on it or opening it via the action menu, the previous filter values are not set again.
Even worse, when adding a second filter and having the filter on a date with 'between' operator as the first filter, the previous values are not set for the second filter when clicking on it. I made a GIF to show this problem:
Don't set the first filter to a date filter with 'between' operator and don't click this filter when changing other filters (hard to explain to users).
Replace the between filter with 2 filters, one on 'less than or equal to' and one on 'greater than or equal to'.
Is this a known issue?