I am currently working on a project where I have created an overall assembly with multiple sub assemblies. At periods of time the main assembly will have an error that it says comes from one of the sub assemblies. I have checked the mates in the top level assembly and they don't seem to be the issue, and when I open the sub assembly and force rebuilds I can't get any errors (or in any of its configurations). The only thing I can think of is the sub assembly that typically seems to be the issue contains a derived part which won't rebuild when I force rebuilds on it, or any of the assemblies it is located in. I can only get the part to rebuild by forcing a rebuild on the part it was derived from. Any help, or ideas would be appreciated because I can't seem to get rid of this bug, and I'm not sure if its a consequence of having a large assembly, or if I have a genuine problem I need to take care of.