@whiscard, peeking at the code, I see that there is some jQuery code which would not work with Reference Application 2.x.
Someone would need to make some code changes to fix this bug; do you have dev capacity for this? (If so, then someone can give pointers as to what changes need to be made.)
You can test out the form in the legacy UI to make sure you’ve configured things correctly (and verify that the bug is in the 2.x refapp UI).