Hello. I am working on a Raleigh from the early 70s. The rear cassette doesn't rotate well -- lots of resistance. I took out the axle and cleaned everything and re-greased, but no improvement. I then figured I'd need to take the cassette off but it looks like someone else tried that and tore up the lock ring (see picture). Any hope for getting it off? And if I do, what do you think could be causing the resistance? Thank you.