Please check the following.
1. Do you have multiple account login in your browser? If so, log out, delete cookie/caches and relogin.
2. Is there a symbol in the form field title? (For example,?, #, -,!) In this case, submission errors can occur. Remove the symbols via form editing.
3. If there is an error in Google Sheet, it may not be synchronized properly.
- If the name of the first row of the form field title is not the title of the form, or if the order of the form field and the column order of the sheet are different, or if another column is added between the columns
- Invalid data on a cell, such as double lines or blank space on non-item rows.
* Note: Google Sheet can be removed using duplicate / space removal: https://gsuiteupdates.googleblog.com/2019/05/new-sheets-features-may.html
4. Create another NBS Form and see if the issue is reproducible.
If the issue still persists despite the above, please back up your sheet by making a copy and contact our NBS support at firstname.lastname@example.org ask for 'reset' so you can start over.