Blank page while printing

[meijin4]

Hi,

Our GLPI is v10.0.17 and plugin is v3.0.0. We use the mail collector to create tickets.
Recently signatures of our users changed, a new image was added and since this moment, when we try to print a ticket that came from an email, it shows a blank page.
We have this in php-errors.log each time we try to generate a PDF.

Our signatures are managed by Letsignit.

Any idea why this would be blocking?