In a server those who join and have low or unstable ping or rates (sometimes even in LAN connections) do not receive the proper knockback that is normal. This can lead to players having unequal abilities and is unfair in PVP matches. This can cause problems with knockback generating devices such as player TNT cannons and knockback-enchanted weapons.

I have experienced this in the LAN world I open to my friends, they can knock me back a full 1.5 blocks without sprinting, but I can hardly knock them back a single block. This created an issue that when locked in head to head PVP, my friend is able to hit me far more easily than I can hit him.

This problem varies a lot, sometimes severe and sometimes none at all.
This problem may be an issue that cannot be solved as well.