help debug contact form on 1.4.0.8

[Abh]

I haven't worked on the website in years and it's probably my fault the contact form is not working properly. 

The email arrives with a few empty fields, email address and message do show.

contact_form.html looks ok for my language, it contains Phone: {phone}, but the received email is just Phone:

I've checked with dev tools and the data is being sent as it should.

Where can I look to fix this?