This bug is not excusively related to tooltips about drag and drop of windows between viewports, but also to other general type of tooltips.
For example, when I switch from a workspace containing a terminal windows to one containing firefox (with this page open) I get a persistent tooltip on the panel saying: Bug #356702 in libwnck (Ubuntu). "tooltips
stick when they shouldn't" - Mozilla Firefox
This bug is not excusively related to tooltips about drag and drop of windows between viewports, but also to other general type of tooltips.
For example, when I switch from a workspace containing a terminal windows to one containing firefox (with this page open) I get a persistent tooltip on the panel saying:
Bug #356702 in libwnck (Ubuntu). "tooltips
stick when they shouldn't" - Mozilla Firefox