Everybody with some experience with BizTalk Server knows that sometimes the ODX files get garbled and have to be fixed manually. I’ve had situations where the compilation of an orchestration works fine, but when viewing the orchestration in the visual studio designer, there are shapes with the red icon of error in it. When things like this happen, or you get those strange “Errors exist for one or more children”, what you can do is have BizTalk re-generate the code part of the ODX.
To do this, edit the ODX file in notepad, and look for the string:
#endif // __DESIGNER_DATA
Then, carefully remove all the text after this line and until the end of the file. Save the file and re-open it in the Visual Studio Designer, and make some change to is (such as adding a newline in an Expression Shape). This will cause the full re-generation of the code part of the ODX that follows the string above, and it will probably fix your strange problems.
An old hint, but a useful one!