Wall Sweep line weight problem

[patricks]

I have 2 different wall types, one with metal studs and one with block, and both wall types have the same split-face block wainscot sweep in the wall type. The problem occurs when both walls are in line with each other (wainscot sweeps align) and I join geometry, then the wainscot on the block wall type changes to a thinner line weight in plan than the wainscot on the metal stud wall, even though both of them are made from the exact same profile and are of the same material. What am I missing here?