Hi Nir!
Thank you for let us know this.
This seems to be a special problem occurring on your site, we have not realize this kind of problem yet.
The error message comes from WP core (not from our plugin), so this is too few information to identify the problem.
Please give us the following information:
What WordPress and Woocommerce versions do you use?
When does the problem occur? When you open the product editor page or when you save it?
Please send us the full error stack (usually it is appears in a table below the error message)? It is very important to see which part of the program call this Printf WP function.
You can also send us a screenshot.
If you give us this information, we can investigate what is the reason of the problem.
Thanks in advance.
Peter