On attempt to delete a VPS from OA the following error message thrown:
Host #XXX is in deleting state.
There are unprocessed (or probably canceled) tasks, related to this VPS.
Check OA Task Manager for unprocessed\canceled tasks, related to this VPS - either use subscription ID of the VPS owner or vps_operations_XXX queue. Cancel tasks that are not needed, run the ones that are supposed to remove the VPS.