I was able to get it to work. I dropped the top of the wall below the roof line and dragged the wall to the inside of the roof as well. This seemed to help. I feel the top of your wall was too high so the base of your wall was attached to the roof instead of the top of the wall. Hope this helps.
You can Attach Top/Base to Reference Planes as well. Detach All, drop the base of the Wall a bit, draw 2 Ref. Planes Elevation for the Top and Base Targets and then use the Attach Top/Base Tool, picking these 2 Ref. Planes as targets - not the roofs.
...FWIW: you can always Edit Profile too. More than one way to skin a cat. 😉
workarounds I know some... but was not supposed to do that kind of behaviour.
This is the only thing that can be done without reprofile wall. But it came with redo the wall joins if the wall begging at lower level. this is a "buggy" behaviour.
Besides, the wall, even if top is below roof line still attach with base, not top.
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