TinyMCE not saving content – js errors

I am using Page Builder by SiteOrigin (ThinkUpThemes compatible) v 1.3.1

The TinyMCE widget has stopped saving new content. My existing instances of the widget display content correctly, but I cannot create any new instances nor edit previous ones.

Running SCRIPT_DEBUG did not fix the error but displayed the following:

Notice: Undefined index: text in /wp-content/plugins/thinkup-panels/widgets-builder/tinymce/tinymce.php on line 36

Notice: Undefined index: text in /wp-content/plugins/thinkup-panels/widgets-builder/tinymce/tinymce.php on line 41

When trying to edit a TinyMCE widget, the javascript console in Chrome displayed this:

Uncaught TypeError: Cannot read property 'open' of undefined load-scripts.php?c=1&load%5B%5D=hoverIntent,common,admin-bar,media,wp-ajax-response,schedule,autosa…:4
thinkupshortcodes_init_slider panel.js?ver=2.10:51
Deprecated TinyMCE API call: <target>.onBeforeSetContent.add(..) wp-tinymce.php?c=1&ver=4104-20140822:20
3Consider using 'dppx' units, as in CSS 'dpi' means dots-per-CSS-inch, not dots-per-physical-inch, so does not correspond to the actual 'dpi' of a screen. In media query expression: print, not all, (-webkit-min-device-pixel-ratio: 1.25), (min-resolution: 120dpi) wp-tinymce.php?c=1&ver=4104-20140822:10
Uncaught TypeError: Cannot read property 'getContent' of null thinkup-builder-tinymce-widget-siteorigin-panels.js?ver=1.3.1:31

Thank you for your input. Any help is greatly appreciated.

https://wordpress.org/plugins/siteorigin-panels/