You're talking about things that are built by us, to test things that we're not even sure if they work correctly. Let me ask you something, with anything in life, regardless of what it is. Whether it be your phone, your gaming system, computer, medicine... whatever. At any given moment your phones screen can crack, you tv can black out, your computer can crap out, medicines can give you all kinds of side effects that can potentially lead to something worse. If we can't perfect things like what we use on an every day basis. What in your right mind thinks we are actually aware that these things are working exactly how they are supposed to. Hell our justice system still uses the god damn lie detector as a viable option(claiming that it works 90% or however much they say it works. Do you believe that too? Just because they told you?) Anyone with common sense can tell you a lie detector is only correct 50% of the time.
I say that to say this... what makes you think a scientist has it completely figured out? They study all their lives trying to prove their theories, but somewhere down the line they could have been wrong in their thesis. They aren't perfect, they are just going off of what they believe. I hate when people say science is the end all be all, it's just simply not. They've proven to be wrong just as much as you think that they are right.