This issue seems to be related to jQuery 3.5.0. It is a breaking change that affects many plugins. Temporarily reverting to a previous version of jQuery (like 3.4.1) fixed the issue for me.
Source: jQuery Issue #4665
Update:
jQuery 3.5.1 reverts the breaking change and should be safe to use.
Announcement: jQuery 3.5.1 Released: Fixing a Regression