As per title, can get a "DisconnectedContext" error/exception during toolwindow left-click drag operations, if escape key is pressed to cancel the move.
1) While dragging a tabbed toolwindow out to become a floating window
2) While dragging a floating toolwindow over other toolwindows/docksite/whatever such that docking overlays are visible
And probably more cases...
Couple things to note:
Drag operations do seem to end up cancelled afterwards, even after the error. Also after the exception occurs, internally something seems to be in a kind of error state, and can get further exceptions after a while even without any interaction.