A rare but annoying issue occurs if an Isogen backing sheet has a corrupt block. When isogen creates the final drawing the text $DDT_AUDIT_GENERATED is generated (usually very large an easily noticed) in the finished Isogen drawing. Lucky this is an easy fix and is confined to the backing sheet DWG file.
Open the isogen title bock then run and audit (by typing A-U-D-I-T in the command line) and purge (by typing P-U-R-G-E in the command line). Once complete save the file (save the file back to the earliest version available which is required for isogen).
Once saved all new isogen drawings will not have the $DDT_AUDIT_GENERATED text.
Running an A-U-D-I-T and P-U-R-G-E will also correct this error on non-AutoPLANT isogen drawings.