If you set the nbt of an arrow to {damage:0.0d}, then the arrow will bounce off of the shooter and possibly any other players. It will also bounce off of any mobs who just recently took damage (ex: @e[nbt=!\{HurtTime:0s}]).

If this was working properly, the arrow would behave the same way regardless of the damage it deals. The targeted entity would always absorb the arrow, even if it doesn't take damage.

How to recreate:

1. Create a repeating command block with the command, /execute as @e[type=arrow] run data merge entity @s {damage:0.0d}
2. Summon a flaming, nonmoving creeper with the command, /summon creeper ~ ~ ~ {NoAI:1,Fire:10000s}
3. Shoot the creeper with a bow. Shoot when the repeating command block is running and when it isn't. Compare the results and see the discrepancy. Notice that if the command block is running and the arrow hits the creeper while the creeper is taking fire damage, the arrow bounces off. If you turn off the command block, the arrow will never bounce off.

Note, this bounce bug is not because of some lag caused by repeating commands. If you time it right, you can execute the data merge command manually while the arrow you're targeting is still in the air, and you'll get the same results.