If you summon a skeleton using "/summon" and you replace the bow with the HandItems tag in this command:

/summon Skeleton ~ ~ ~ {HandItems:[0:

,1:{}]}

He will constantly try to draw his bow over and over but he will never fire it.

Steps to reproduce, summon a skeleton with this command:
/summon Skeleton ~ ~ ~ {HandItems:[0:

,1:{}]}

Then just aggro him, he'll start spam drawing his bow.

This guy seems to be having a similar issue: MC-87841