Client having issues with digital signature filed in form

We have 2 forms that utilize the digital signature field, the Client Informed Consent Form, an the Client's Agent Informed Consent Form. Both are working fine for me (Mac + Safari/Chrome) but the client is getting an error notice that the digital field has not been completed (even though it has). Not sure what the issue is, though I am guessing it is a browser/compatibility issue. Any help is greatly appreciated. 

I have tested your form and was not able to replicate the problem. Here's a screencast:

I also cloned the form and tested it on an Android mobile device:

Perhaps the problem is a conflict between your embed code and your website's resources? I see that the embed code still uses HTTP, which suggest that its been awhile since this was embedded on your website? Could you please try to re-embed the form using the iFrame embed code instead? Here's a guide on how to get that code: https://www.jotform.com/help/148-Getting-the-Form-iFrame-Code 

See if after re-embedding the form will fix the problem in your client's end. Would it also be possible to know what device and browser he/she is using? We'll wait for your response.