I assume that by "overwrite error" you mean the "Metdata conflict warning" , and when you click on it you get this - see screen shot:
This is an old bug in Lr. Do not be concerned about your images. Your images are absolutely fine because Lr saves every step you do instantly and automatically in the catalog.
In addition to this saving to catalog there is an option (it's an option and not necessary for the function of Lr) to save the metadata to file. This is primarily for people who want / need to see the Lr edits in Adobe Bridge. Bridge cannot read the Lr catalog, but only the file. This makes it necessary to <save metadata to file>. The error message - it's actually not an error, it's just a hint - means that the data in the catalog and the data in the file are not completely identical. Since Lr always goes by its catalog - unless you do a <read metadata from file> your images are safe and sound.
You can stop this message by doing this:
Go >Edit >Catalog Settings >Metadata tab and uncheck the box <Automatically write changes to XMP>.
After this Lr will stop saving metadata to file automatically and the error message will not appear.
If you want you still can save metadata to file, albeit manually. Either by going >Metadata >Save Metadata to File, or shortcut Ctrl / Cmd + S on your keyboard. You can batch save by selecting any number of images in the Grid View and hitting Ctrl / Cmd + S.