Have seen this issue in 3 interactions now, 2 chats and 1 ticket in which any changes made on their Customizer doesn't get saved when clicked on the Save Changes button. The settings go back to default.

Steps to reproduce the behavior

(In one of the issues we encountered so far) This is when changing the Colors settings in the Customizer.

1. Go to Appearance > Customize.
2. Click on Colors & Background.
3. Click on Save Changes.

What I expected to happen

1. When I make changes in the Customizer, the changes will be displayed on the Preview section and these will remain the same once the changes are saved.

What actually happened

1. Once the Save Changes button is clicked, everything resets back to default thus the changes made are not applied on the live site.

Context

So far same issue happened on these three other interactions.

Browser / OS version

Is this specific to the applied theme? Which one?

No, so far themes in which the issue is observed are Gema, Dynamic News, Morden, Karuna

Does this happen on simple or atomic sites or both?

So far only on Simple Sites

Is there any console output or error text?

None.

Level of impact (Does it block purchases? Does it affect more than just one site?) Yes

Reproducibility (Consistent, Intermittent) Leave empty for consistent.

Screenshot / Video: If applicable, add screenshots to help explain your problem.