ISY Integration: Deleting integration doesn't delete half the entities

I’m experimenting with ISY Integration and need to delete everything and start over but am finding that deleting the integration leaves thousands of entities behind. How can I mass delete (just) those entities?

Note that if I try to select them all on entities page before deleting integration (so I can filter on the integration), it tells me it can only delete about half the entities. And if I delete the integration first then I can’t filter on it as it is not there for me to filter on (yet half the entities still exist - all in unavailable status).

I should mention that I have a large ISY installation. There are 2627 entities so when I talk about half of the entities I’m talking about roughly 1300 entities. Not something you want to have to delete one by one.