Riley-

Tested in Chrome, Edge and Firefox, occurs in all of them. Chrome and Edge console error output: ``` index.js:1 Uncaught TypeError: Cannot read property 'replace' of undefined at $Ie (index.js:1)...

Upgraded to grapesJS `0.16.34`. The error is still present in `^0.4` of `grapesjs-mjml`. As you've mentioned it is likely related to `mjml-browser`. Not sure if this helps, but some more...

I, too, have this issue and have moved back to `0.5.3` as a result (resolved the issue). I do not use session middleware, but the error was thrown when using...