Most likely, openseadiver, uses CKEditor for WordPress plugin for visual editor. Such incompatibility problems occur and I, but they are likely to come from CKEditor for WordPress, judging by the reviews on the plugin page with the latest updates than by Page Builder by SiteOrigin. I ask the developers to consider compatibility issues are two plug-ins (for simultaneous operation of two plug-ins can not switch from html mode in visual, have to disable CKEditor for WordPress).
This review hasty, you could ask for help and solve the problems.
Greg Priday, continue to develop the plug-in – this is an excellent development that is worthy of appreciation.