Hi
One little Question:
Do the Artefact look something like those on this Topic?
If Yes or No I would always recomment to verify your ETS2 Files on Steam if you encounter an Error.
Go to your Steam Library
Right click Euro Truck Simulator 2
Go to Properties
Then Local Files
and then click on "Verify Integrity of game files..."
This should then check if there are any errors in your files and redownload them then.