Baking and UV errors

hello! i’ve been trying to figure out where i’m going wrong since switching to 2.8 (I dont recall it happening in previous versions, but I could be mistaken) but when I’ve tried baking a pair of materials on an object, I get this proboem


not only does the texture get throughly jumbled, but the second material doesnt get baked into its UV space at all. I’ve looked through a bunch of tutorials and can’t find what I assume is the obvious mis-step. anyone able to help?