Mismatched Signatures / Browser-dependend Signers

Hi. I received a PDF that has been signed on the Adobe Sign platform. That's what the digital seal tells me. Unfortunately there are no personal signatures in the PDF, so the question is: How do I find out who has signed the document? The only hint I found is a URL that has been included in the document where the (analog) signature is. The URL looks like this:

https://salesforceintegration.eu1.echosign.com/verifier?tx=HEREISALONGID

Unfortunately the result of opening this URL raises more questions than answers:

- in Firefox 68 ESR the page tells me that "John Doe" from Adobe has signed the docuemtn

- in Chrome 83 the page tells me that Person A has signed

- the analog Signature on the document is from Person B

I know Person B, but I don't know Person A. So in the end I cannot find any (digital) proof that Person B has signed the document. And seeing different signers on the Adobe page depending on the browser with which I open the URL is totally weird.