Whenever Implants, which increase Movement Speed (Muscle Replacement) are added, you slowly glide into the ground and get an Error Message saying "Invalid Move player packet received" and are only presented with the option "Go Back to Server List". Same goes for the Sprinting Speed Implant (The lung one, of which you can put multiple in), but it only occurs once you start sprinting. When loading the world again after that it stays as well though.

Those upgrades only changes the base game monster attribute. You probably have a buggy mod messing around with gravity and such.

Here are the Mods I have:
https://imgur.com/a/he9RPXz

Start removing mods until you find which one is causing that interference, starting with Galacticraft and Morph.

It actually was none of these, but Thaumic Arcana (Thaumcraft Addon (Biomancy)). To be honest, it seemed kinda buggy in the Thaumonomicon and is no longer being developed. I removed it.