Project Import blocked due to missing Custom Field Select Option values

Summary

Unable to proceed with Project Import due to errors on Custom field options. As an example:

The custom field 'Environment' requires option 'Staging' for the import but it does not exist in the current JIRA instance.

Steps to Reproduce

1. Have a source instance that has a Single-select custom field with multiple contexts. (Eg. Environment)
2. Set up target instance to have the same contexts and custom field options
3. Perform Project Import from the XML backup
4. The project import can fail in certain cases

Expected Results

Every project import will go fine

Actual Results

On certain project import, it can fail in certain cases. The below can be seen in the UI under custom field section:

The custom field 'Environment' requires option 'Staging' for the import but it does not exist in the current JIRA instance.

Notes

One of the trigger is when customfieldoption.customfieldconfig does not match fieldconfigscheme.id but the relation relies on fieldconfigschemeissuetype table between fieldconfiguration and its fieldconfigscheme.

Workaround

Refer to: https://confluence.atlassian.com/display/JIRAKB/Custom+field+values+are+not+imported+using+Project+Importers+Tool