Thank you for the response.
I disabled all plugins except the MEC plugin and the Fluent add-on. And I enabled the default “TwentyTwenty” theme, but the problem persisted.
I also noticed that [on iPhone] although the “more events” icon does not appear on days with events when I click the “view next month” arrow button, they will appear after I scroll on the page far enough in either direction that calendar goes out of view.
It seems scrolling the calendar out of view on my iPhone causes it to reload the event data.