It seems like I need to implement some kind of Large Hadron Collider to detect this bug
I think that would require a really really 
Large Donate Button, so I'll keep trying. I might be in alternate universe today (how can we ever really know?), but here are some different results. Each of the attached shows a movie/series record after updating...
- the record (for a known update status);
 - the people needing updates (some or all links disappear);
 - the record again (missing links return).
 
The behaviour continued with series (as illustrated by the first two screen shots) until I ran out of records needing updates. It continued with the first movie I tested (third shot), but then stopped (fourth shot)—sort of. I was still able to find a few, but they seemed rare.
So now we know...
- It happens.
 - It stops happening. Maybe. For movies.
 
It's not much, but it didn't cost $4 billion. 

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