Will the rewards be paid automatically or will all token accruals be made manually?

Rewards will be processed via smart contracts

Can you manually block payments that are already in the smart contract?

Blockchain transactions can't be blocked or stopped after they've been confirmed

Can artificial intelligence make an erroneous transaction?

In general that could be possible, but blockchain tech confirms all transactions

But you can mistakenly send a different amount of tokens and they can no longer be returned