Well title says it. Noticed it in one game that after upgrading my Necronomicon 2 to 3 the item appeared to be useable (off cooldown) but wasn't useable. After a certain time I could summon the necronomicon warriors again and everything was back to normal.

Sadly I can't reproduce it and it was some time ago so I have to look through my games which it could have been.
Anyone else noticed that problem on one of another occasion?