Steps to reproduce the issue

1. In a custom Joomla component, define a field in the admin form like so:

   <fieldset name="modulepositionset" label="Select Module Position"
             addfieldpath="administrator/components/com_modules/models/fields">
       <field name="moduleposition"
              type="moduleposition"
              label="Select Position"
              description="Choose a module position." />
   </fieldset>

2. Navigate to the admin backend and open the form.

3. Click the "Select Position" button rendered by the moduleposition field.

4. Observe the error.

Expected result

• The modal should open showing the list of available module positions, allowing the user to select one.
• The field should work outside com_modules, particularly in custom components.

Actual result

• An error modal appears with the message:
  COM_MODULES_CHANGE_POSITION_BUTTON
  An error has occurred.

• The URL of the modal includes an invalid or non-existent view:

  index.php?option=com_modules&view=positions&layout=modal&tmpl=component&function=jSelectPosition_
  

• When you remove &view=positions, the modal loads successfully:

  index.php?option=com_modules&layout=modal&tmpl=component&function=jSelectPosition_
  

System information (as much as possible)

• Joomla version: 4.x / 5.x (tested on both)
• PHP version: 8.x
• Server type: Apache/Nginx (doesn't seem to affect this issue)
• Browser: Any

Additional comments

• It appears the moduleposition field is tightly coupled with com_modules, making it unusable in custom components.
• The error is caused by a broken modal URL pointing to view=positions, which doesn't resolve outside of com_modules.
• Removing &view=positions from the URL allows the modal to load correctly.
• Possible solution: make the view optional or adjust the field to handle a fallback if used outside of com_modules.