Cannot import grades when using non-numeric scale

I cannot import grades when I am using a non-numeric Scale. I have a scale with 3 items (Not Attempted, Attempted, Completed). These are the steps I have taken to import the grades:
1. Graded one student
2. Exported the file to CSV
3. Altered the exported file to include the other student's grades
4. Import the modified file
5. Throw my hands in the air when reading the error message 'Supplied grade is invalid'

This error also occurs when using the Satisfactory/Not Satisfactory standard scale although using numeric scales works a treat.

Attached is the error I am getting with other screen shots of the Custom scale I was using at the time and file import preview screen. I have found a temporary work-around as outlined below but that is not really ideal
1. Change the grading in each Moodle assignment to be out of 3
2. Alter the csv file to have the grades 1, 2 & 3 (3=being Completed; 2=Attempted & 1=Not Attempted)
3. Import the file
4. Change the grading in each Moodle assignment back to your custom scale