cable tester says line is broken but I still get gigabit

Hey all,

I've been fixing the network of a certain location. It was a mess. A lot of wires had to be repatched and a patchlist had to be made. While doing this I've been using a cheap wiretester to check all the wires and determine which patch goes where.

There were a lot of wires where my tester claims that at least one, sometimes multiple connections failed on the cat5e cables. The numbers were mostly 2 and 6, but 3 and 4 were also up there. Even tho the tested results, I could still get gigabit (measured) over those lines.

How is this possible? As I understand 1,2,3 and 6 are crucial for a connection. I'm guessing the tester is fucking up, but how come? It's been good to me for at least a year now.

Looking forward to your idea's because it's been messing with me for a couple of days now.