I saw this had been reported, and resolved earlier with MCPE-10159, I apologize if I am wrong to report this as a new bug. It is unclear what was resolved with the earlier report.
Anyway, If you have an enchanted bow in your inventory as well as a normal undamaged unenchanted bow. Craft a dispenser and the enchanted bow is used.
Thank you for your report!
I can reopen MCPE-10159 and apply 1.0.4.11 as affected