There is an issue in Chrome with drag and drop functionality when moving around activities inside a course. Sometimes when attempting to reorder activities, the basic drag and drop functionality stops working. Often when this happens, the selected activity will become ‘stuck’ to the cursor and will not properly release. The activity will follow around the cursor and will not properly drop into place even when you release the mouse button. You have to click again to force it to drop the selected activity. When it finally releases and drops, it often appears greyed out and doubled on the page. Once you turn editing off, these changes are not saved and the activities revert to their previous order.
This issue was noticed on m35 sites, using Clean theme.
Also tested several previous releases of Chrome on Browserstack and the issue still persists. This behaviour seems very random and inconsistent, so testing has been difficult.
The versions of Chrome used was version 70 and then tested versions 68 and 69 on browserstack. All versions had issues with drag and drop, although behaviour was random and inconsistent._