seems to be a problem in 2017. Width mate errors. Sometimes i try to do a width mate in an assy and there is no error showing but the mate just does not work. Part just sits there in the same location as before the mate was applied. You can move the part just as if there was no mate applied.
Also tried a sym mate using a plane and 2 flat surfaces with same result. In the past if a mate was not able to be created you got a warning, now this seems to not be happening. Or is it just me?