The message “This element could not render due to invalid markup…” is caused by the
textarea element and I believe this is a bug so I’ll post this in our issue tracker so this will be queued for further investigation by our development team and if found to be a bug, they will release a fix for this in one of the succeeding updates.
Regarding scripts, it should be accepted by the Raw Content element. There could be a bug in the Classic Raw Element why it outputs the actual code on Firefox. I’ll report this as well. For now, please use the Raw Content element and not the Classic Raw Content. Alternatively, you can move your script to the Page JS. Just DON’T include the
Hope that helps.