Only first damage type is checked in combat instead of picking the most effective.
Steps to Reproduce the Issue:
Pick Sagani's "Masuuk Hunting Bow" (it has 2 weapon damage types: pierce / crush)
Atack any creature with different DR against crush and pierce damage
In my case it was Forge Knight (DR: 12, Pierce: 15, Crush: 12)
During attack damage formula was: My Pierce damage VS Pierce DR.
It should pick most effective damage type, but my damage was compared to piercing DR.