The bugs are fixed at revision#67530. 

The reason is:

We have to synchronize a lot of stuffs after just finished Eiffel compilation (EB_MELT_PROJECT_COMMAND.tool_resynchronization). At this point, UI changed, so the docking dragging event is aborted. Now we cancel the dragging event, if Eiffel compilation is just finished and end user is dragging a zone for docking.

Thanks for your report.