Dear Sid,
This mostly happens when male heads are installed in the field for a modular ended cable. The inexperienced person installs the pairs straight across instead of following the T568A or B wiring scheme. This will cause a "split-pair" failure See this url for the correcting wiring. Use either T568A or B, not both in the same cable.
http://www.cabling-design.com/references/pinouts/t568ab.shtml
Split pairs on jacks are caused typically when the white halves of two pairs are swapped, but the mix-up would have to be identical at both ends otherwise you would have seen an "open" or transposed failure first, It's not just continuity, it is balanced pair continuity.
How this does actually happen is first: testing showed the two "whites" transposed; second: The repairer picks the wrong end and now transposes that end, which; third: fixed the continuity problem but now resulted in "split-pairs".
Sincerely,
Joseph Golan, RCDD
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