There were some problems with the site after the WP 5.8 upgrade on July 22, but the site seems to be working now.
Regarding the Event slider, the incorrect Date/Time still appears randomly. This happens event after clearing the WP cache with the GoDaddy (Managed WordPress -> Flush Cache) menu option. Flushing browser cache afterwards also does not help. I don’t believe there are any other cache plugins being used.
Do you have any other ideas? I’m afraid we may have to replace this Slider with one from a different vendor.