A customer of ours had recently some troubles with this feature, as well. We didn't find this working anywhere, and found out that the issue (in version 1.0.5) is caused by a malformed jQuery element & class selection in Signature.prototype.initUI setup function.
We've made the attached changes in order to get the component working, but please not that it is unlikely that this will allow it to be used multiple times in the same page - since the jQuery selection is not designed for such requirement.
Works also on 1.0.4 (Outsystems 9.1).
Thank you for the solution Pedro!
Pedro Gonçalves wrote: