I get 999: There are more than one survey elements named 'field_24_0' (case-insensitive) in the section named 'understory_layers_and_approxima'.
This is the offending question I have tried tweaks such as replacing 1-2 with 1 or 2; >5 with > 5
It sounds like you have more than one field with the name same in your form. Not the options but the actual name of the field. Check that or post the form.