I've really done it this time. (Or was it the guy that isn't here anymore? No PDM to trace it back) Well regardless, it's up to me to do something useful with it. 

Install Ref. Version 2018 SP3.

Now that I'm revising a tank spool balloon detail drawing created 7 months ago, I notice that it has changed from its original intent and content. In five similar drawings, each with seven sheets (1 per spool), and each sheet with a BOM to express and detail what is shown there, the QTY of every single component in every BOM is -. Not zero, not one, not any integer. A hyphen.

This puzzled me greatly. I had changed what was present in the views, but the BOM was not updating at all. During a tech support call with our VAR, I stumbled into the cause by opening an archived original version of the drawing. Every sheet could not find its configuration, and they each reverted to configuration Default (which contains everything).

Somewhere along the process, someone (it may or may not have been me) destroyed the configurations and replaced them with display states. This breaks any drawing which used those configurations. Do it over.

You can link a View to a Display State. You cannot link a BOM to a Display State.

OTOH, if you want your quantities to show a hyphen and not update contents, but retain component links, then destroy the configuration its view was looking at. I don't know why you'd want that, but that's how to get it.

TL,DR Summary:

Issue: BOM shows hyphen for a QTY. Contents do not update. Balloons still reference its contents.

Cause: Configuration no longer exists.

Resolution: Recreate configurations. Relink View and BOM to new configuration.

Lesson: DON'T DESTROY ASSEMBLY CONFIGURATIONS.

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