Also, they don’t have as much to lose if they’re caught accepting a bribe. If a career politician is caught accepting a bribe, their career as a politician is over. But if a mechanic is caught accepting a bribe during their 2 year stint as a representative, they would suffer minimal reputational damage and could just go back to being a mechanic.
You also mentioned that you could prevent this with harsh penalties and long term audits, but I think it would be pretty easy to circumvent an audit. Like, if I wanted to bribe someone elected by sortition, I would just offer them free stuff instead of money so it’s harder to trace. Like free hotel stays or prepaid gift cards.
I could imagine apolitical people treating a sortition win like winning the lottery and expecting to get money out of it. And just auctioning their vote off to the highest bidder.
With all that said though, there would be a lot of advantages to sortition so the risk of corruption and bribery might still be worth it and would still probably be better than our current system.