I am experiencing a delay dragging between interface windows in Media Composer 2018.12.7 on Windows 7 and 10.
The "pointing finger" drag cursor doesn't turn into the "arrow with a plus sign" drop cursor for several seconds, and only after one wiggles the mouse. Otherwise, you cannot drop the item while the cursor is still the "pointing finger."
This happens when dragging items between bins, when dragging bins into folders in the project window, and when dragging clips to/from the composer window.
Creating a new user setting initially solved this. I had created new users on multiple machines, and the bad behavior eventually creeped-back to multiple machines.
I figured out that this would start happening after Exporting. I had recently started using the Avid Media Processor regularly.
I just discovered that in a brand new user setting, I can cause this behavior by changing the untitled default Export setting use the Avid Media Processor, and performing an Export.
When the Avid Media Processor is the selected Export method, I get the cursor-change delay when dragging between windows. When I switch the active Export setting to QuickTime, there is no delay dragging-and-dropping items between bins or the composer monitor.
I have not yet determined if I can keep Avid Media Processor export settings stored in user settings, and just keep them inactive when I do not need them.