The code looks ok so my guess is starting your field names with underscores. This page says it is not supported and it is not good practice. I would start there. Surprised it published really. Hope that works
Changing the fields did not resolve the situation
@IsmaelChivite & @JamesTedrick do you think you guys can have a quick look?
I just noticed this as well, I don't have underscores or numbers starting my field names. The choice filter does use numbers as the options though.
The form I was looking at doesn't usually get used on the web, but I was trying something because of another issue I'm having and noticed it. (Also seems relevant doesn't work properly on the web form..)
I was looking because I have a search() appearance not listing any options in my web form, just the option in the choices itself, it works in the app though.
Update on this.
The problem is in the choice_filter column. You should not use quotes:
After making this change, the web app is happy. See below: