This violin came into the shop with the fingerboard detached. This is a common problem that I see in the shop.
It's hard to say what causes it happen. I can assume there are a few reasons. Here in Utah it can become very dry, which causes wood to shrink. That may lead to the glue joint coming apart. Or maybe it just took a hard enough hit to pop it off. Maybe a combination of both... I sometimes wish I could see these things happen.
The good thing about violins is they're meant to come apart for repair, and it's a pretty straight forward fix. It took a few minutes to clean and prep the fingerboard and neck. Then it was just a matter of gluing and clamping.
Once the glue dried over night. It just needed to be restrung and set the bridge to the proper location. It should be good for many years, and the customer was very happy...