You have a problem with the blue and/or brown pair in one or more of your terminations. Even if the wire is properly seated in the groove, look for nicks or breaks in the conductor where you stripped the outer jacket off, or maybe you accidently had the tool reversed when you punched the wire and it's cut on the inside, not the outside, or if you reused an end, check that the original wire didn't leave some of its plastic behind in the groove preventing a proper punch down.
You have a problem with the blue and/or brown pair in one or more of your terminations. Even if the wire is properly seated in the groove, look for nicks or breaks in the conductor where you stripped the outer jacket off, or maybe you accidently had the tool reversed when you punched the wire and it's cut on the inside, not the outside, or if you reused an end, check that the original wire didn't leave some of its plastic behind in the groove preventing a proper punch down.