Upgrade Deletes Layout Content

As the topic says, every time we do an update we loose all the content in the layout (custom html, settings, ext…).

I have tried to export/import the layouts, but it doesn't seem to work. What am I missing?

By the way, that was 4.1.5 to 4.2.0… I assume 4.2.0 to 4.2.1 will also do the same.

I have upgraded my sites from 4.2.1 to 4.2.2 without any loss of layouts.