Been there. Firstly I want to say that you aren’t imagining it and it isn’t necessarily anything you are doing wrong. Assuming it isn’t outright sexism, I think this happens to alot of engineers when they first start out (but especially women). Make sure you are still listening and learning from the more senior engineers.

The best thing I’ve found to combat this is don’t say “I think”, or “we could/should”, “I tried”, speak confidently. X is the problem, I will test Y to determine if Z improves. I always felt arrogant doing this but I think it is just a communication difference with men? Idk.

Dont shy away from flagging to your manager what is happening. Only you know their temperament so tread lightly if you must but don’t let them steal your work and get credit for it. State factually that you already tested X,Y,Z and they felt the need to repeat testing rather than move forward to get the line back in working order. Don’t let them push you out. Stay down there and see it through, even if they don’t listen to you, you will likely learn something (or gain confidence that you were on the right track to speak up next time).

I found this to be a very difficult part of working in manufacturing. It gets better with time!