Arrows that were shot by a bow that is enchanted with a punch enchantment do not remember their punch property when being unloaded (for example by logging out).

How to reproduce:

1. Get yourself a Punch II Bow and some arrows

/give @s minecraft:bow{Enchantments:[{id:"minecraft:punch",lvl:2s}]}
/give @s minecraft:arrow 64

2. Place two dirt blocks beside each other in the air so that there are four blocks space between the floor and the blocks.
3. Go into survival mode if you aren't already
4. Shoot an arrow with the Punch II into the underside of each block.
5. Stand below the first block and mine it so that the arrow falls and hits you.
6. You will be thrown away quite a bit.
7. Log out.
8. Log back in and wait a few seconds because the player is invulnerable for a few seconds after login.
9. Stand below the second block and mine it so that the arrow falls and hits you.
10. When the arrow hits you, you will be knocked back only a little (as much as a normal Arrow does).

This behavior is expected since there is no NBT-Tag implemented in which the punch property is saved in.