strange code line on invoice

Hello,
i have a problem with the invoice downloaded from the back of the website, it shows me 3 pages of code lines that overwrite the product name, code and price.
The strange thing is that the same invoice to the client is perfectly clear, the problem is only in the invoice downloaded from the order in the back of the website.
You can see the invoice at the link.
Can you please help me??

Thanks
Giulia