You have a drawing you suspect is corrupt and you want to try and clean it up.
Drawings can get corrupted if you have a bad crash.
First type AUDIT on the command line then Y to fix errors. Also type -PURGE on the command line, then type R, and hit the enter key and set to remove all unused regapps.
Secondly try a Recover with Xrefs. Close the drawing, click on the “C” Button at the top left of screen / Drawing utilities / Recover with Xrefs and run through the process.
If neither of these work then we can try a Wbock. Open the problem drawing and type WBLOCK on the command line. Set the button at the top to entire drawing and set the save location at the bottom.
(Include Map information if prompted)
This will create a new drawing called New Block.dwg.
Then open a new clean blank drawing using your usual template. Then in the is new drawing type INSERT on the command line, click the browse button and browse to the New Block.dwg created above. Untick Insertion point, Scale, and Rotation. Tick on Explode.
In many circumstances this will clean up a corrupt drawing. Save the result. Test the drawing.
You can then re-import any Layout tabs by right clicking on one of them and using ‘From Template’ as below:
This is a last resort file recovery, so things like xrefs and data shortcuts will need to be re-established.
Hopefully that will have fixed the drawing.
(If this still does not work then then you will be into data recovery mode, slowly copying objects from the broken drawing into a new one until it breaks your new drawing. Then you will have identified your bad objects that need remaking.)