Update, for what it’s worth.
Over summer, and after getting the place properly watertight the wood gradually straightened out. It’s not perfect but getting there and all bay one of the sills are pretty much acceptable.
I think the problem was that the underside of the wood was more humid than the top side which could dry out.
Lessons are: don’t expose wood to repeated large changes in temp and humidity over a prolonged period. If you do however, be patient, there’s a chance that it will fix itself.
So glad I didn’t panic and replace them.
Remember that you are also interviewing them. They won’t expect you to know all the answers, but will want someone that they can work with. If you can, answer questions with the STAR method (situation, task, approach, result), but don’t waffle. You can use one piece of experience in a variety of ways: teamwork, research, urgent deadline etc.
It’s ok to say that you are nervous, they should try to put you at ease.
You may be asked ‘trick questions’, these are not usually to to you up but to see how you work an unknown problem. There is no right answer. Not knowing stuff is ok. Not being able to think up a plan is less so.
Remember whatever the outcome, this is really useful experience. See if you can get a site tour, ask about the tech used… You can then add this to your knowledge for later. In my experience, industry is frequently several years ahead of academia so you get a good chance to understand the real world.