I've always found Lucas wiring to quite sound in design and manufacture - where it all falls apart is the total lack of attention that most of it receives - until some extension cord havin' HACK dives right in and starts re-engineering.
Case in point - I had a very early production MGB that had only amassed about 50K miles on the clock due to "continual electrical problems" according to the previous owner. Once home with the car, I removed enough speaker wire, lamp ballast wire, Romex (!) wire, Scotch-Locks, wire nuts, toggle switches, HOUSE light switches, balls of masking tape, balls of electrical tape and random other bits of sh!t to fill a milk crate. Once back to the original wiring, cleaned, repaired and checked out - the ONLY fault was that the grommet on the left front inner fender, where the wiring passes through to go to the headlight, was displaced and the high-beam (blue / red trace) wire had rubbed on the cars body creating a short to ground. This was the ONLY problem that I found with the harness - other than the jackass that had BEEN working on it ........
It's a known fact that Lucar connectors are a bit sketchy - and that every termination that ISN'T a little tiny brass screw will turn green if the humidity is above 4% ... but the REST of the stuff is pretty good ......