can not change header image

Hi,
I started a new webiste with Tiny Framework as theme.
I followed the instructions on the comprehensive guide for a custom header image on each page.
On the wordpress dashboard I set a different image for each page but it still shows the same image on every page. The images can not be the problem because I can use them in the customizer but with the same problem of course, … same image on every page.
What am I doing wrong?