I haven't been able to try this more than once yet, but what happened in my current playthrough is that I accidentally hit the "attack" convo choice when I came to the ring, but then decided to make a run for the pedestal thing to see if it would let me still fight. I paid the 150gold, and it did indeed put me in the ring. I ended up losing though, which, strangely enough, cost me a life and sent me to the death plane or whatever it's called.
Anyways, might want to make it so you cannot activate the control pedestal if you decide to attack the slave guy. It was frustrating for me to not be able to fight for the ring like I meant to, but losing a life was much worse

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edit: oops looks like I posted this in wrong bug section, should be under Tome4.