OK.
Sounds like either a sync issue - so the object is not yet ready at the point you're trying to use it. In which case, you should put some sort of checking step in before you try and use it.
Or ....
Your mapping is not tight enough and it's failing to identify something at runtime. If this is the case, it could be anything in the object tree for "NameMapping.Sys.Kasse.ArtBei.DBText12". If any of the components are not available, it will fail as you're describing as the object at the end of the tree can't be found. One bad link breaks the chain.
I have no idea what "shape1" that you mention in your original post has to do with any of this? What you're describing sound like a standard "object not found" type problem.