Sudden Critical Damage? WTH?

Have never had this happen before. Close to 500 hours played.

Fresh morning, zero moodles, plenty of good gear. I'm walking through a nearby forest to get to some houses, conserving energy, avoiding trees, and I suddenly get "Critical Damage," my health is tanking.

Absolutely has to be a bug. What mods could possibly be causing this? I do have a good handful of mods running.