I use a different logo on a Page Header to make it more visible against the chosen header background. This works great — whenever the page with this Page Header loads, the default logo is overridden by the one chosen in the Page Header settings.
However, if I upload a Mobile Logo in the customizer (Layout>Header>Mobile Header>On) the logo I chose in Page Header no longer loads on pages where the Page Header is used. Instead, the default logo displays.
How to replicate:
1. Upload a default site logo.
2. Create a Page Header with a different logo.
3. Load a normal page and see the default site logo.
4. Load a page that uses the Page Header with a custom logo and see the alternative logo.
5. Switch on the Mobile Header and upload a mobile logo.
6. Reload the page with the Page Header with a custom logo and you will see the default logo rather than the custom logo originally chosen.