@Marcin Jackowski Thanks for reaching out to us, product team acknowledged this issue and already reached out to portal team for a solution.
The issue happened when display form only for few locales (de-DE, en-US, es-MX, es-ES, fr-FR, it-IT, ja-JP, ko-KR, pt-BR, zh-CN) but not for en-GB. A workaround temporarily would be to display the display results without showing the errors for the unsupported locales.
I will update to you again if there is any update, thanks for reporting this issue.
I hope this helps.
Regards,
Yutong