Hello folks, Have been trying to sort this problem for last couple of weeks with some limited success, first up I would say it may not be a Thunderbird issue but need to eliminate this along the way. Problem relates to simple drag and drop functionality within Windows Explorer, selecting a file from right hand pane then left clicking before dragging to new folder location would cause unpredictable results, typically grabbing a whole tree of other folders and moving those too, the exact same problem applied to Thunderbird when moving emails either individually or as a group. Desktop PC running Win 10 Pro, it does have a fancy graphics card with competing drivers, uninstalled everything and reinstalled with a clean install - this resolved the problem (so far) with Windows Explorer but puzzlingly has made no difference to Thunderbird, options tried so far include: Using a different mouse Selecting 'click lock' from mouse controls - this works but it does feel a bit awkward Using another email client Outlook for desktop, doesn't seem as pronounced but still a bit awkward. Reverting back to Windows basic default graphics driver, all works as should but looks terrible Has anyone come across this behaviour before? Thanks