Boolean union B fail yet one is mirror of other

Why does this simple union fail ?

Both A and B fail in my project file.

maybe the item is sharing same face at base.

so I nudge it down a bit, then it works, then I boolean difference it with my cutter (one I had originally trimmed A and B to match base) and now the Boolean Difference fails.

How do I get these A and B to union ?

and then after pasting in the cutters for this forum file, I try A again and it unions !!!

so then I try for B as its a mirror copy AND IT FAILS.

Grrrrrrr !
Boolean union corners fail.3dm (1.6 MB)



Hello - so far it seems to all work OK here.


You have to fillet the edge:

Edge problem.3dm (799.8 KB)