Uploading hand-signed contract failure

I can't upload a copy of a hand-signed contract to the esign system.  This is a new error as in the last two months I have been able to do this 6 times for other contracts.

It uploads and you see the green flash saying:

.... but then almost straight away the following message is sent and it gets cancelled by the system.

"We were unable to create your agreement Signed PCR&CCS2016 British Mini Club 9-440 for because of a problem adding signature fields to it."

I have tried uploading it as a pdf and as a jpg - both open fine on my PC and are no larger in size that other documents I have previously uploaded without issue.

I have checked your guides and I am uploading them correctly.

I have tried over the last 3 days about 10 times in case it was a temporary problem... but it is still not working!

Why won't the system let me upload a hand-signed contract anymore?

Hope you can help

Alison