Selecting timeslots in RadScheduler on webpage initially scrolled down results in timeslot offset

[Anders]

When I select timeslots, using the left mouse button and dragging, those timeslots will be incorrectly choosen on a scrolled down webpage.

The screenshot is attached.

This picture shows the end of a mouse drag operation, starting with the timeslot above the current one, so 2 timeslots should have been choosen (instead of 6).

Why? What can I do about it?

This question is also asked on

https://stackoverflow.com/questions/53871128/selecting-timeslots-in-radscheduler-on-webpage-initially-scrolled-down-results-i

 

[Anders]

This question has got very low attention or is not understandable so I have added two screenshots to the Stack Overflow posting already mentioned in an edit section. Please tell me what I can do.