To redo this Bug:
1.Get a Bow
2.Put it in your Offhand
3.Press F5 two times
4.Hold right mouse button
Expected: Bow lifts up (usually)
What happens: Bow looks down (not usual)
Environment
Windows 10 Home 64-bit, Java 8 1.8.0_25 64bit, Intel(R) Core(TM) i5-4210U CPU @ 1.70 GHz 2.40 GHz, NVIDIA Geforce 840M/PCIe/SSE2
Duplicate of MC-88356, if you have not, please use the search function in the future to see if your issue has already been reported.