Please update your version to the latest one. Some improvements related to this issue have been made in version 5.0.0. Not half a second, but enough to distinguish moving and editing.
When you test it and the issue will still occur for you - let me know, and maybe I can help you in some other way.
Unfortunately currently such feature is avaialble only by modifying the inner code of the dhtmlxScheduler.
We’ll try to solve this problem in the future updates.