The runaway loop detection stuff is designed as per thread singletons (TLS). The worker threads don't properly reset the runaway counters.
Create a new anim BP.
Add a large number of steps (blends, etc.) in the Anim Graph.
Set "bEnableUpdatesInWorkerThreads" to true.
Create a new SkeletalMeshActor and set it to use the AnimBP.
Let this play for a long period of time.
Expected: No warnings
Actual: Runaway warnings
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-33946 in the post.