A block appears with this message if it seems to have more than one source. This is a rare message that points to a bad build or to bad CAD sheets. The message means that more than one block exists in the module with the block number indicated.
Sometimes this creeps in when someone uses a spare block and forgets to take it off the "boneyard" page. We do not know what happens in this situation. It is certainly possible that it is often harmless.
Duplicate source for Module 1,13,13 Block 160 on 11313 CIS07 14D04 TU only
This error can be built directly into Hyperview. For more information, see the article Building error reports into the M14.