Hi,

Thank you for the feedback, We will fix this issue in the next update ASAP.

In the meantime, you can apply the below quick fix and recompile your assets with Gulp or webpack.

Go to src/sass/vendors/plugins/_fullcalendar.scss after line 187 add the below code:

// Popover
 .fc-popover {
 .modal-open & {
 z-index: $zindex-modal - 1 !important; 
 } 
 }