Yes, I am aware that WP changed TinyMCE and Connections was updated and brought into alignment back on June 2nd/6th with versions 0.8.10 and 0.8.11.
Connections 0.8.14 is the most recent and compatible with WP 3.9.2.
Although it may be possible that there is some bug in Connections which is only affecting your setup. It is still more likely that the source of the error is being caused by another plugin even if that may seem unlikely. Other plugins, if not update date such as TinyMCE Advanced, Mail Poet and Advanced Custom Fields can cause this error on other pages. That is why I suggested deactivating all other plugins, so that possibility can be eliminated. It is part of troubleshooting the issue.
Another quick question, what other Connections extensions and templates do you have installed and what version numbers? Form and/or Link specifically. I’m fairly certain they can not cause the error in the dashboard but I’d like to establish that you have the latest versions installed to eliminate them as a possibility.