I am using Fullcalendar timeGridWeek side by side with dayGrid.
I can drag between the two and resize or drag in the timeGridWeek (the one on the left).
However, the problem is functionality is broken after hour 6PM or towards the end of the day, depending on the screen width.
I've also enabled clicking on time slot. I can click until 13:00. Anything after that stops working.
If I set the #container > * element to 1600px (on my ultrawide display) everything works correctly.
I can't figure out why.
I also have this running in a React App with MaterialUI and it behaves in the same way. I presumed it was something to do with the theme, but now can see it does the same thing with minimal styling.
Codepen: https://codepen.io/anon/pen/exabpW?editors=0010
Apparently it's a confirmed bug: references here
https://github.com/fullcalendar/fullcalendar/issues/4503
and here