OP is having problems and troubled by escrowed funds held by third parties such as bounty managers because the owners of the token themselves change the smart contracts of their own tokens. That means previous tokens are becoming useless and worthless. So it somehow makes the use of escrow useless as well.
That is indeed a curious case and important question and I guess the only possible answer is by providing the escrow with equal amount in USDT or some other stable coin such that in case the escrowed tokens are taken back by fancy changes in the smart contract they can at least pay the bounty hunters in USDT and compensate for the loss.
Is there any case of such happening? I haven't seen this happen anywhere but this is a good question and want to see if this ever happened and more importantly how it was tacked if it happened in past. Please share the link for any campaign where this took place if you know any of them.