In eme_calendar.php, the DIV that contains the random calendar ID, which is appended to the output in line 474, is never closed. This results in invalid HTML, and as a side-effect, if the user switches the month by clicking the arrows next to the month name, all article content below the calendar disappears. Solution: add a line 502 with the content
$calendar .= "</div>\n";. Observed in WP 4.9.8, plugin version 2.5.32, Yoko theme. Frankly, I’m amazed that this doesn’t seem to have been reported before.