[Bug]: Formstack genius crossword form doesn't always show a submission confirmation

[abeddow91]

We've been having some complaints in relation to this form:
https://guardiannewsandmedia.formstack.com/forms/genius_crossword_248

Which you can see embedded here:
https://www.theguardian.com/crosswords/2024/feb/05/genius-crossword-no-248

Users are no longer receiving a confirmation that their entry was successful, see below screenshot:

Formstack recommending embedding the form in an iframe but this is already the case. Further investigation is required.