Suppose we have two issue types 'Support Request' and 'Production Incident'.

For the Production Incident I have created a custom field called 'Problem Manager'. This is a required field. The Support request issue type does not have this field.

When a user creates a Production Incident, the Problem manager field is asked and mandatory (required). [correct]

When a user creates a support request it is not shown [correct]

When a user changes the issue type of this support request issue to production incident, the problem manager field is not shown and the issue can be saved as a production incident without a problem manager. [incorrect]