I worked as a supply teacher. I've had lots of deaf students over the years so I'm used to working with CSWs and interpreters.
So I went to a class where the interpreter told me, "X doesn't understand why she has to do this again" so I explained, in English, that 'no she didn't need to repeat the work she had to do something slightly different" It was looking at life stages and she'd missed one stage out.
Anyway the interpreter ignored me and repeated that, "X doesn't understand".
So this is repeated and then I turned tot he interpreter and asked her to interpret what I was saying. I was very polite about it.
I received a mini lecture on how not all interpreting is simultaneous and she (the interpreter) knew what she was doing.
So I asked her to interpret again what I was saying, she sighed and signed to X. BUT she didn't sign what I was saying. So I signed to X what she needed to do and why.
Interpreter was furious, the CSW who I didn't know was a CSW because she was sitting on a computer shouted that, "I saw her do that"
I just thought the terp was having a bad day and didn't think much of it.
I got to my next lesson with a different interpreter and we recognised each other, we finally worked out I'd interpreted a conference she had attended a couple of years previously.
While I was teaching the first interpreter put a complaint in to HR. I'm not sure what she put, but she was not impressed with me.
The following day I saw the second interpreter who, unwittingly was an angel, and had discussed with terp1 how experienced an interpreter I was and how well I interacted with X.
I was sent a message that terp1, "would not take the complaint further as long as I didn't complain about her".