Errors in console when loading web UI

[cwBrendan]

I have Mailsac setup on an Ubuntu server. When I load the web UI in a browser I receive a number of errors in the console. I also receive similar errors when I attempt to check an email (which does not work). Here is the error:

Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:335:11)
at ServerResponse.header (/opt/mailsac/node_modules/express/lib/response.js:718:10)
at ServerResponse.send (/opt/mailsac/node_modules/express/lib/response.js:163:12)
at done (/opt/mailsac/node_modules/express/lib/response.js:957:10)
at Object.exports.renderFile (/opt/mailsac/node_modules/jade/lib/index.js:374:12)
at View.exports.__express [as engine] (/opt/mailsac/node_modules/jade/lib/index.js:417:11)
at View.render (/opt/mailsac/node_modules/express/lib/view.js:126:8)
at tryRender (/opt/mailsac/node_modules/express/lib/application.js:639:10)
at EventEmitter.render (/opt/mailsac/node_modules/express/lib/application.js:591:3)
at ServerResponse.render (/opt/mailsac/node_modules/express/lib/response.js:961:7)
at exports.errorHandler (/opt/mailsac/lib/middleware.js:102:13)
at Layer.handle_error (/opt/mailsac/node_modules/express/lib/router/layer.js:71:5)
at trim_prefix (/opt/mailsac/node_modules/express/lib/router/index.js:310:13)
at /opt/mailsac/node_modules/express/lib/router/index.js:280:7
at Function.process_params (/opt/mailsac/node_modules/express/lib/router/index.js:330:12)
at next (/opt/mailsac/node_modules/express/lib/router/index.js:271:10)

This started happening a few weeks ago but nothing has changed on our end. Any idea what might be causing this and how to fix it?