How do shields work?

[Sliske]

I just bought magic shield and have been using life shield for a while now but in Yuri's boss fights sometimes I defend against all 4 magic orbs and procs 4 times with the shield, sometimes I get hit for 15 each but if I don't use a shield I get hit for 8. What is going on?

[Ryaka]

No idea but that was happening to me too, I just stopped trying to block them and dodged them instead haha.

[Aunt Floof]

Its because when you use a shield and block an attack, she flinches and for a small second, loses the shield, thats when you get parry damage on yourself if you get hit.