I know I am, but think I'll probably still do it.

[Binding]

I do some part time work. Occasionally I take on some extra. I don't especially want the extra hours or money, but if I'm free I'll do it to help out.

Last time, I took on something outside of my normal role and, imo, was unfairly critised. It wasn't perfect, but it was a decent first attempt imo. It wasn't constructive feedback, it was "having a go" criticism.

So, I've been asked to do another one. This is also outside my usual role, but closer to what I usually do. I could do it, but I'm not inclined to help out after what happened last time.

But, the person who gets the headache if I don't, isn't the person who criticised my last effort. That person will, however, overview it again.

see I have no idea why people do stuff to help out. if you don't need the money, do it if you want to, don't if you don't. Simples. Me? I'd probabaly not do it or have put your overseer back in their box the first time they were rude to me.
PS I voted YABU for the agonising over it.

It's not at all unreasonable to turn down work that you're not contracted to do. You would be entitled to turn it down for any reason at all.

If you are having to pitch in and do extra work that you are not qualified for or trained to do, that means your dept is most probably grossly understaffed.

Also, whoever assigned you the job should have outlined their expectations and closely monitored you at all stages in doing the task.

The fact that you were then criticised for a passable job (provided any changes required were indeed minor) is bad personnel management.

The worst thing is that other personnel were copied in on the criticism.

I would have responded to the email outlining the above points (and would have copied in all parties).

I wouldn't do it - they can bollocks.

I was in favour of raising it with the person asking you and the critical manager. But then I read this and thought, hell no. I would say no and explain why.