This might indicate a poor head/haft fit, actually, the heads are forced on mechanically and they gouge into the wood and are a pain to remove sometimes.
I had a similar one and it seemed ideal until the wood shrank a bit and it was a terrible fit, a properly shaped haft fitting a cleaned out eye would have just slid up higher and seated tightly as the wood shrank slightly. Also good reason to leave the 3/4 of an inch or so of handle above the eye instead of chopping it off.
The head should be able to slide down fairly readily when force is applied like Fortytwoblades says, perpendicular to regular cutting force, so you can remove it to clean it stuff, and if you are throwing it, handle hits will cause the energy to slide the head off instead of breaking it.
OK done yakking.