I don’t think this is limited to interpretation, but when you’re an interpreter the worst type of pressure to feel is when you know there are other equally or more qualified interpreters in the room, and you know they’re judging your every word. Honestly it’s the worst, well actually the worst is when they butt in (never do this! It totally throws people off their game!), but what I see it as is a lack of trust in the interpreter to do their job.

If you can see that they truly are struggling, then maybe you can offer help, but even then you should prioritize having a quiet word afterwards. The irony is that although you may not trust their ability, you first have no choice but to trust them to give their best so that they can develop their skills. Not trusting them only gets in the way of their development, and in that case no one wins.