Galaxy - API First Training - Can't complete section in Step 4: Author Examples

Im trying to complete this subtask in Step 4 of API First Training.

Having removed the name property in the response body of the GET example in the mock collection I then validate the linked mock and click on ‘issues found’ where the issue is identified correctly …

It recognises that name property must be re-added. But selecting ‘Confirm changes to collection’ I am repeadtedly getting the following …

Can someone help me identify the problem?

Collection: ‘Customer docs’:
https://www.getpostman.com/collections/80cdfdbc8b57166e86e6
Collection: ‘Customer mocks’:
https://www.getpostman.com/collections/474f6afc201581ec38be

Many thanks