Looks like he switched to DP Calendar
I was looking into this in the yootheme booststrap,php they made a change to the onload template class.
templates\yootheme\vendor\yootheme\theme-joomla\bootstrap.php
from 2.7.16
'onLoadTemplate' => [
ThemeListener::class => 'loadTemplate',
ChildThemeListener::class => 'loadTemplate',
CacheListener::class => ['loadTemplate', -20],
],
2.7.19
'onLoadTemplate' => [
ThemeListener::class => 'loadTemplate',
CacheListener::class => ['loadTemplate', -20],
],
I am not having the issue on yoo theme pro ver. 2.7.16 so if folks need to go back it might help