This also happened when I had much fewer arrows (around 20).
ERng> gath ar
None of your containers could possibly hold the weight of the resulting bundle.
You gather 13 arrows into a single bundle on the ground.
ERng> get ar
You pick up a bundle of arrows.
ERng> stow sho
You put an oak shortbow into your backpack.
ERng> get ar
You remove a bundle of arrows from the hip quiver you are wearing.
ERng> bundl
You combine all 51 of your arrows into a single bundle in your right hand.
ERng> put ar in qui
You put a bundle of arrows in the hip quiver that you are wearing.