The Welcome email is deleted every time

In Subscription > Welcome email, I selected "New email" in the dropdown, customized and save an message, I checked if works and everything is ok here, but time after, the Welcome email configuration just disappear, the "Standar email" is selected and the message that I configured is erased. In Settings and messages > Welcome I have the default configuration:
https://i.imgur.com/uDd3Gme.png

In other way, how I can do a backup of the Welcome email? I don't see and option to save as a custom template or something similar, just the save option in the "New email" field.

Thanks.