Buggy cutteray lower yield than expected

Having recently acquired a Focus buggy cuttery Mk6. I was excited to use on the one hardest to farm resources: Cobalt

I was ready to yield 400+ per node (stats showed 398 for erytherite and I have level 2 vehicle mining perk). However, when I do farm them, I only get 323 per node. I'm not sure if i'm doing something wrong?