Yep. You can't have that loop. There can be only one "relationship path" from any given table occurrence (such as from Out_Outgoing to In_Incomming) to any other table occurrence in your relationship map.
The key term here is "table occurrence". You are not limited to one "box" (called a table occurrence ) for any given table. You can create as many occurrences as you need. Thus, you can resolve the issue by either making a new occurrence of IN_Incomming or a new occurence of OUT_Outgoing and now you can link your tables without getting that "loop".
Useful links to help you better understand how to deal with this: