With the release of V2.8.6 and V2.8.7, there can be an issue with the size of the signature field. There is something in the CSS that makes it look like the signature is only allowing about 1/2 field area to be signed. The actual issue is that the background is extending past the end of the field.
To get around this issue, add this to your frontend css:
.cm-hipaa-form-signature {min-height: 100% !important;}