When nodes that require tail processing are finished and their outputs need to be disabled, they're placed on finished list that gets processed on the main thread to disable its output.  The can cause downstream nodes to start tail processing and disabling its output too.

Soe both the tail list and the finished list get updated together in complicated ways.

Simplify this somehow.  It's really hard to keep track of these two lists and when the get updated and when they should be cleaned out.