We have Nintex Workflow for SharePoint 2013 on prem. Nintex is preventing me from saving a site as a template. I get an unknown error. How do I get around this without deleting my workflows (as I would like those copied in the template as well)? Should I de-activate the Nintex workflow then try saving the site as a template again? Will that delete all of my workflows?
I would suggest exporting your workflows first and then try deactivating Nintex. Nintex itself should not restrict you from saving the site template, but I can say that your workflows aren't copied as part of the template definition for the site. So exporting them will be a good step regardless the outcome.
The error may be caused due to a content type of something bugging out during the saving of the site template or space issue for the site collection, so take a look at those as well.