Mirrored bones and IKs, ends up doing opposite rotations for no reason When I mirror my bones, IKs, etc.. (even when reseting rotation beforehand) they end-up rotating oppositely (cf. gif).

(https://gfycat.com/equalmaleamericancrocodile)

And nowhere can I find anything to fix it, it's driving me crazy! Even more so when I feel like it's simple and I can't seem to find the way.. Please help me if you can, and thank you in advance to anyone able to give me any insight :)
Object>Apply>All transforms to deltas. Check that first. Then check you are mirroring accordingly in EDIT mode of the armature (check the wrench icon property tab to the left of the screen) and/or the tool's settings on the top bar in the viewport. Mark the correct axis.