When using this mod and medieval weapons, every shield stop working and you take all the damage

This issue has been resolved on MedievalWeapon's end

Can you post the link to the medieval mod here?

The most straightforward way to add a shield is to redirect a function call with Mixin:
https://github.com/rikka0w0/MobZReborn/blob/5b067930d58e0a65ecb28f2b0600eabf06fccb0f/fabric/src/main/java/net/mobz/mixin/PlayerEntityMixin.java

Many mods do this, but it makes these mods mutually incompatible with each other.

I think something is wrong with this:
https://github.com/Globox1997/MedievalWeapons/blob/cabfaa96cd0b7ae56c7c619320e238d6b31309f6/src/main/java/net/medievalweapons/mixin/PlayerEntityMixin.java#L44-L50

The link of the mod: https://www.curseforge.com/minecraft/mc-mods/medievalweapons
The issues with fabric shields lib: Globox1997/MedievalWeapons#60

Looking between these mods I'm not sure if there is a good way for me to resolve this issue on my end.

A video of the issue

Looking between these mods I'm not sure if there is a good way for me to resolve this issue on my end.

You don't need to do anything on your end, I believe it is MedievalWeapons' bug