Prepopulate Phonenumber in Mautic-Form

Hello there,
i´m creating the gdpr routine for the rights of to be forgotten etc. Therefore i created a campaign with a form, which is prepopulated will all data in Mautic. But unfortunately only text fields are working. Phone numbers are blank. I can update the number, but after a site refresh the field is blank again. Everything is setted up in the form itself, like the text fields. Has anyone an idea how to let phone numbers appear permanently if the populate feature is enabled?

Thanks for your help in advance.

I can confirm that. If the field type is phone its not filled. Its only filled on field type text. (Mautic 3.0.1)