Problems with ‘Round Corners'

Hi everbody,

First of all, sorry for my bad englisch. I'm German

Here's my problem:      step 1: i'm writing a word and then i'm using the effect ‘create outlines‘ in the type menu.

                                  step 2: after that i'm using the filter ‘round corners‘

                                   But not all corners are round after that. I've problems with the letter ‘S‘. Just 2 corners are round and the ohter two are                                    unchanged.

Does anyone know what the problem could be?

Thank you very much!

Simon