Can you confirm if this is a bug?
I think the bramble casters are not stacking with shield-blocking DR.
Did a test in pvp where I went in the corner to shield-block, once with bramble casters equipped, and once without them equipped. Both times I had a blocking DR of 19. I do know that before mod 7, it did stack and I could get shield-blocking DR of 29 against arrows with the bramble casters equipped.
Any response would be appreciated.