Hi Heiner, did the tuned up version attached above work better for you then?

> and used loft to connect the lower and the upper shape.

I tried repeating this step, and it appears that the loft in its default mode is not making a quite accurate enough fitted result to get it joined properly.

But it does appear to give a good enough result if you set the option in Loft for "Profiles : Exact".

So probably if you delete the side wall parts for the problem letters and build new ones with that "Profiles: Exact" option turned on, it will probably fix it up.

- Michael