When configuring field dropdown in JSM form that is attached to a request type, if you link the dropdown to a Jira field and make the field as required and set a default value.

Steps to replicate: 

1. Create a JSM Form, attached it to a request type
2. Create a dropdown field, link this field to a Jira custom field
   1. Note: this should be a static dropdown field, Asset field, User field, label field, etc are not included
3. Make this field required
4. Select a default value for this field
5. Save form
6. Update this dropdown field, link this field to another Jira custom field
7. Save form

Expected behaviour:

• In Request Create, this field should be required, and should trigger validation with errors upon submit
• default value should not be present as the defaultValue for the field in template form
  • https://api.atlassian.com/jira/forms/cloud/<cloud-id>/servicedesk/<servicedesk-id>/requesttype/<requesttype-id>/form

Actual behaviour:

• In Request Create, this field is not required, and does not trigger validation with errors upon submit
• Invalid default value is present as the defaultValue for the field in template form
  • https://api.atlassian.com/jira/forms/cloud/<cloud-id>/servicedesk/<servicedesk-id>/requesttype/<requesttype-id>/form

Workaround:

• In Project setting → Edit form
• Delete the form field
• Recreate the form field and link it to Jira custom field again
• Save form