If you add a multi-image field to a collection, you can no longer export the collection. You get ZERO records. I understand that that field is an array, and can’t map to a one row export.
At the minimum Webflow should export all the other data, while it works on a solution. The export should also throw an error to the user when the count exported is not equal to the collection count.
The workaround is to tap the API for the records, where you will get everything.