Frequently, when updating objects that appear early in the editing history, projected sketch lines will lose their link to the updated geometry, causing cascading failures throughout the assembly. There is currently no mechanism for telling Fusion "The line you lost is here now", so trying to repair the assembly is nearly impossible.
Fusion should have an interface for clarifying any lost projections, misplaced joints, and any other references to geometry that might have changed due to edits to the history or changes to externally linked models.