What's your hlog like now? Ive just seen one that you posted a while ago which looks rather strange.
It's not a usual sharp dip like you'd expect to see for a bridge tap, but those very slight waves could indicate signal reflection on the line. Using the standard calculation for a bridge tap (160/MHz) then the start point is somewhere around 320 feet. Because its so slight it may not be picked up on most tests, and tbh Im not even sure if Openreach would class that as a full blown fault.... but it could indicate a copper impedance mismatch, which in turn would cause the line to throw errors.
The echo effect may show up on a JDSU which could give the engineer a more exact reading for distance. If he can see it on the JDSU then it may give an indication where to look, there's several things that could cause this; but in view of how small the bumps are IMHO slight corrosion on a joint is probably most likely, but it can even be caused by damp weather.
It's looking like one of those stupid faults which is hard to track down until the line begins to get real bad. I sympathise, been there, done it. Seen an engineer try work his butt off to track down the problem because standard tests pass.
It's very important to remember that hlog log is a capture of a moment in time, so you'd need to see this over several hlogs before drawing more definite conclusions.
Others may have some thoughts on impedance mismatch and what could be a small signal reflection showing in the lower tones from that one hlog.