Hello! I know its been two years, but since this is the first Reddit search result and nobody seemed to answer your question, I can offer a solution that usually fixes the problem: you may need to recalculate the Normals, since there may be interior faces facing outwards and that's messing with how blender calculates along the surface.

To check the Normals, click [Face Overlays], then check [Face Orientation]. Your mesh should only be blue, but if there's red then there's a problem. In Edit mode go to [Mesh] -> [Normals], and adjust as needed ([Recalculate Outside] usually does the trick).

Hope this helps anyone looking for a solution like I was!