I'll start off first by saying that I was able to temporarily fix this by re-installing Chrome, and that the issue only affects this users computer (I logged into their account from a second computer using the same version of Chrome and it did not experience the issue). I tried on their system in another browser (IE) and did not have the issue, so that's a third confirmation that it's Chrome based.
When trying to drag and drop an existing booking to a new slot, it simply does not resolve the drag and drop. Normally when doing the drag and drop there will be a small clock popup that shows the start/end time changing, and that does not change on this users Chrome.
Any thoughts?