Hi, 

When working with viewports, (in existing files) I can edit directly the custom scale property typing the value directly, once this is written, the viewport scales the image and the value previously typed, stills in the cell ✔️:
 

But for new files, I cannot do the same, and when a set a specific value on the custom scale field, the viewport scales the image, but the cell displays zero ✖️:

Does someone know how can I fix this?

best regards!