Part moves without input

Hello! I was working on a rather large assembly and I needed to angle one plate in relation to another. To do this I lined them up and then did an Angle Mate on the top of each plate and then put in the angle of 14 degrees (the angle needed). It angled the plate downwards and I continued working on the assembly.

As I inserted more component and continued working, I noticed that the angled plate was no longer angled downwards but was instead angled upwards and the 14 degree Angle Mate still existed. I hadn't touched the component or interacted with it or anything mated with it for some time.

I'm not sure how this happened and would appreciate any help! Thanks!