These are the steps to prodocue the error:

1. Create a customfield (any field). As an example: User name
2. Create a search filter containing that customfield (Ex: Project = "Test" AND User name = "user01"
3. Save that filter.
4. Rename the customfield. Ex. From User name to Username
5. Access the previous filter and the filter will not show any result.

To prevent this, you can change the JQL query from User name to the custom field ID (IE cf[10010]). However, it is not user-friendly for customers who are preferably using the simple search.

It would be convenient for all the users if the simple search feature on the Issue Navigator uses the custom-field ID from the beginning rather than the custom-field name. It would definitely make changes to the custom-field's name more adaptable.