Do the bolts have a reduced height head?

If so, you should grind the chamfer off the socket. Some sockets have a significant amount of chamfer that reduces socket to bolt head engagement. In fact, I grind off the chamfer on all of my sockets even for regular bolts. When a bolt head is rusted, it is usually at the top, a socket with a heavy chamfer doesn't grip a the base of the head so you are left with a very narrow band of grip.

And, as the sockets wear, grind off more to access a less worn spot.