Some arrows shot into a block never despawn

Arrows shot from skeletons and (likely) infinity bows as well do not despawn over time (didn't test infinity because I don't have it yet..). Normally, these dissapear after 5 minutes of sitting like any dropped item, xp orb or similar entity. These count as entities in the world, so they can contribute to entity lag like that of item frames, minecarts, glitched items or other things.

The server I've been playing the snapshots on has a skeleton farm within the spawn chunks (meaning that the area is loaded 100% of the time). After 2 days or so of this farm being used briefly after 37b release, roughly 700 arrows have accumulated there since skeletons can see through the corner of blocks sometimes, depending on the block and angle, and shoot at you. Normally this isn't a problem, but the arrows don't despawn.. and it's within spawn chunks, so the lag from them is always there.

The picture with the sky shot is outside of spawn/skeleton farm range, standard entity count of 110ish. The picture with the furnace + chest is within the same room as the farm, but looking away (800+ entities). Proof shot of the skeleton farm is there. And the picture with the dispenser is the most direct shot of the arrows. See those glitched out ones inside it? Yeah, 680 or so. You can also see the fps drop, which I didn't really look at until now (37 on far to 10 on tiny).