Steps to reproduce:
Create a new page "Restricted", with page restrictions
Create a new page "Child", as a child page of A
Move "Child" somewhere in the same space, where it is no longer a child of "Restricted".
Expected behaviour:
When viewing "Child" there are no longer restrictions on the page.
Actual behaviour:
When viewing "Child", there are still restrictions on the page. Opening the dialog shows inherited restrictions still apply.

Workarounds

Option-1 - Flushing the relevant cache

1. Navigate to > General Configuration > Cache Management
2. Clear Inherited Content Permission Sets cache through the UI.
3. Check the behavior.

Option-2 - Re-applying restrictions on the page

Manually remove the restrictions and re-add them to the page.