"Baltar lied about the results, but the test was real, and worked exactly as planned."
Ok, I'll have to take your word for it. This wasn't obvious to me watching the show, but admittedly maybe I missed a key line.
This still leaves the question as to why it failed to catch Tigh/Tory/Tyrol.
I don't know how much more obvious it could get - Baltar runs the test, "if it's green you're a normal human being and if it's read you're a Cylon," and almost immediately the entire screen lights up flashing red. His Head Six says something like "Congratulations, you've just captured your very first Cylon" and wonders aloud if she'll kill him rather than be exposed. Baltar panics, so he changes the results and lies to her.
As far as not catching the others, they were never tested. Neither Anders nor Tori had joined the show at that point, so they weren't tested. Very few people aboard Galactica were tested, because the test was ridiculously slow - it took something like half a day for each person. And when Boomer shoots Adama a couple episodes later, everyone presumes that since she had been "cleared" by the test, the Cylon Detector doesn't work and it's scrapped.
So if the Detector not catching them is the basis for the writers not being "consistent," I don't see it.
Well, maybe you're right. Maybe my memory is playing tricks on me.
So if the Detector not catching them is the basis for the writers not being "consistent," I don't see it.
It's not "the" basis. It was one among many. Maybe it turns out not to be a contradiction after all. That leaves many others.