Addition of calendar produced ghosting

[bwood]

The site is northeastspca.org. The page is Events. I inserted a calendar with a placeholder that has been working well, until lately. Now on the page you’ll see some ghosting of the calendar. It’s an overlap. It is happening on the larger and mobile variant.
I’ve done the usual clearing cache, and running as adm. I will probably clean this up by deleting the present, and starting the calendar again solving the problem; but I would like to know the cause. Thanks all for suggestions.

-Bill