I am not sure, if you can reproduce that, but it occured to me, that my redis adapter that uses phpredis was not able to delete an item from redis that is of type hashmap when using the method delete() and the correct key. As i changed the method to del() it suddenly worked.
Just wanted to let you know.
I expected the same behavior, but in fact, renaming the method solved the problem. Switching back to it and the hash could not be deleted.
I'll try to setup a small example use-case or something.