I would be very careful, rather get support involved. It might be blocked because of pinned data stuck in cache or some other potential issue that might lead to data loss.
Below are some knowledge base articles on restore blocked LDEV's. But I'll be very careful, but as I said best to get support involved.
or maybe this one, keep in mind this is a article about formatting and deleting data:
I'd like to stress again, in this scenario it would be best to get support involved.