What are all the reasons an assembly might load parts as lightweight?

My v2017 SolidWorks has gone bonkers and now loads every assembly with lightweight parts. That's not what this option says should happen:

An assembly having only ten parts loads as light-weight. This just started a few days ago and I haven't managed to find the secret (other) toggle to turn this off.

Any ideas?

SolidworksAssemblies