I'm using FullCalendar Angular library and i'm facing a problem with the side time mark. When I hover over the calendar, the mark is at the right place (black cross represents where my cursor is):

But when i'm hovering the event, the mark goes back to the top of the calendar :

Here is the css which change the color :
tr:hover td:first-of-type {
background-color: #64B5F6;
}
Like I can't share the code of the calendar here, I'm only asking for reasons about this behaviour which could help me to resolve this.