At the moment, AutoPropagate cannot be applied to locked segments.
We frequently handle translation orders including multiple similar documents. If we want to change a term in a locked segment that appears, e.g., 20 times across all documents, we have to manually unlock each segment and enter the change manually. We encounter this scenario quite often due changes in our terminology.
Not only does this cause quite some effort, it is also a possible source of mistake since you might miss a segment.
From our point of view, it would be great to have a checkbox in the general Studio options allowing AutoPropagation onto locked segments.