Wrench on one nub, or across two like a bar? Could be they have a tool that engages all 4 nubs at once so they don’t snap off, or thing was over tightened.
I’d get a spare bit of wood, press it against one of the nubs, and then smack it with a hammer repeatedly. If you’re careful it shouldn’t stress the nub too much but the vibration may unseize the thread.
It’s solid but not very strong. I tried to use a small wrench and it was breaking the nubs. The thing is incredibly tight
Wrench on one nub, or across two like a bar? Could be they have a tool that engages all 4 nubs at once so they don’t snap off, or thing was over tightened.
I’d get a spare bit of wood, press it against one of the nubs, and then smack it with a hammer repeatedly. If you’re careful it shouldn’t stress the nub too much but the vibration may unseize the thread.