Digital signature change to invisible - Problem

Hello,

Previously, my English is working in progress, sorry after all.

We're signing some PDFs and after insert the second signature, all of them changes to invisible. That happened in specifics pages and i don't have a special detail in that page to happened that problem.

It's better to explain using images. Let's check it out.

At the first image, we had the PDF without signatures.

When we're signing at the first time work like a charm. Look at the second image.

But, after we insert the second certificate at the same page, both signatures changes to "invisible". We can prove that signature are imported through the right panel. It's a sort of visual bug.

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We have some Google Docs which are downloaded as pdf or printed as .pdf with a specific software. Both methods returns a normal file, but we've identified that problem when we're downloading as PDF.

Thank you so much.

Regards.