I thought I would reach out to the community to see if anyone else is having similar issues. We discovered a bug with the Marketo Form not submitting for some users. At first we thought it was a one off case but it started occurring for dozens of individuals for the last 3 months. Marketo Support is aware of the issue and they said they released a patch to solve this issue. However we sent out a promo email for a webinar yesterday and received over 20 emails letting us know the form is not working.
Basically what happens is when individuals fill out the form and submit, it does not complete the action and gets stuck on the "Waiting" label (which is Please Wait). See the below image for an example.