Function breakdown problem

I have created a function (function “Yaw” on the attached picture, transparent one), which was broken down to other leaf functions.
When I have opened project the next day, I for some reason could not go on with adding leaf subfunctions (Capella considers it incorrect action and shows a “no go” cursor when I hover it over “Yaw” after selecting “add function” in the palette).
What may be the problem?

Ok, my fault. Somehow (my guess it because of the way I did transition from OA), parent function “Yaw” was allocated to the external actor, while it’s subfunctions were allocated to the system.
After I removed “Yaw” allocation, everything works fine.

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