Spidertron's knees (or where the legs articulate) are the issue here. They are the "hit boxes" telling the leg to separate. Much like the other enemies in the game were recently fixed, I think spidertron has to be changed the same way. I'm sure Erik will correct me if I'm wrong, but I think that's what's going on here. The hammer makes this one stick out like a sore thumb, heh.
-Cheers