We have debugged the issue at our end and the problem seems to be with Script Loading Marketo forms (forms2.min.js) .
Thanks & Regards
Thanks so much for looking at this issue. Yes, we have seen the forms2.min.js issue on the optimized (Experience B) version of the targeted content. Even if we use the same exact content. Somehow, the Insert Element seems to either change or break form and make the form js not able to find the form name.