The value 0 is interpreted internally by Aivie or Mautic as “empty”, which causes this option to be automatically selected, even without a defined preselection.
Problem
If you use a radio button field (radiogrp) in a form and an option has the value 0, this option will be automatically preselected.
This happens even when no default value is defined.
Typical example:

Result: The option “0” is always preselected.
Cause
The value 0 is treated internally as a ‘empty value‘. This means:
0is interpreted similarly tonullor “no value”- As a result, the system assumes that no value is set
- At the same time, the first option is displayed as the default
This behavior occurs only with the numeric value 0.
If you use a string instead (e.g., "test"), everything works correctly.
Solution (Workarounds)
Option 1: Don’t use numeric value 0
Use a text value instead of 0:
- Label = 0
- Value = zero
or directly:
- Label: “No”
- Value: “0 points”
Option 2: Define a neutral default value
Add an additional option:
- “Please select”
- “N/A”
and set this as the first entry.
Option 3: Set the default value to something that doesn’t exist
You can also configure the field so that the default is not ’empty’ but something else, such as
- Not selected
- N/A
Status
This behavior is known and has been reported as a bug:
https://github.com/mautic/mautic/issues/15966
A fix is planned. However, one of the above workarounds should be used until the ticket is resolved.
Summary
The value 0 is treated internally as “empty” and is therefore automatically preselected. Use a text value instead or add a neutral selection option to work around the problem.

