When FAssetRegistry::SaveRegistryData() is invoked for a umap redirector it will fail the check
check(!bIsMap || (InDependencyType == EAssetRegistryDependencyType::Soft));
Because the redirector itself is a hard link to the umap it references but is considered a map for bIsMap, it will fail the check.
Adding an exception for redirectors which ultimately unwind to a umap with a soft reference at that point should fix the issue.
Move a umap package to a new folder. This creates a redirectory to reference the new location.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-42287 in the post.