I have two cylinders sitting on top each other and they overlap by about 50%. I thought I'd fillet the corners, but solidworks keeps acting like they're two separate cylinders and ignoring the face. See the attached image.

I initially had them overlapping very little, which when we 3D printed it, caused it to break easily at the joint. I thought a fillet would help, but it wouldn't do it correctly. I increased their overlap, thinking that it was a lack of contact surface, but I'm still getting this issue. Am I missing something?