Maya Mirror Weights not working properly

[Deleted User]

Hey guys so I wanted to test out a model with some animation, but I'm having a problem mirroring the weights, I've done it on the left side and ensured the model is symmetrical in world and object, as I've circled but when I try to mirror (no matter what combination of options I choose) it's just distorted and messed up as you can see. Any idea how to solve this? Thanks.