I believe this is a problem that has to do with Kobo. Same form was deployed on ONA and it worked.
It is a Kobo Server issue. Someone once made a similar complaint in the community in 2021 (See link - Error: Import Failed! - User Support / Form Building - KoboToolbox Community Forum). It was fixed by Kobo from the backend.
I think this is a problem specific to Kobo (and not the form) because this error appear even if i take a survey previously deployed and download and upload without any change and the errors repeat.
The problem started 10.11.2023. The same above error is produced with all my forms.
@Josh @Kal_Lam