That sounds unlikely.
Every switchyard has constantly varying loads, but they don't have histories of such failures. Perhaps you saw a result of incorrectly completed workmanship.
Secondly, whether U/G or above ground, such minimal cycling is the same.
Note that any signs of heating in a joint requires immediate rectification, so a lot of care goes into preventing it no matter what the generator source is. So it is normally rarely a problem.
Further, I would question any U/G joints. I haven't heard of any - but I only worked in the Qld industry.