How to properly configure template for Magento 2.3 child theme?

Question

Magento

Greetings,
there is a child theme, based on the standard theme for M2 blank, created in the standard way, as usual.
There was a need to change some elements, for example, move the logo, search, cart, from the header content container to header.panel, and add your custom block to the header content.
In the child theme, in the template folder, I created default.xml, wrote the newly created block in it, and also added the movement of elements -

<move element="minicart" destination="header.panel" before="-"/>

And then a surprise awaited me - it turns out that any change in the default.xml of the child theme leads to such behavior that the top.links links, links in the footer, and possibly something else are no longer displayed. The newly created block and logo are displayed normally. I return default.xml without these changes - everything is fine...
At the same time, if the same changes are made directly to the default.xml of the parent theme, then everything is fine, everything is displayed... But the parent theme cannot be changed, since it has several different children on different storeviews.
Has anyone come across this and what is the reason for this behaviour?