Hi Dave, welcome
I have had this sort of pain, and can still get it, but it is much less of a problem than in the first year or so. I too wondered if it was the end of the spike poking into the bone inappropriately. The funny thing about my pain was that taking weight off that leg (im a climber and runner) would make sharp pain where the loading up had been painless, I can’t imagine how that works because the spike was certainly well fixed, and cementless. My THR is over 7 years old and I am racing half-marathons and jogging ultras, as well as 5k parkruns every Saturday, and the last time this pain made me limp during a race was over a year ago, and it was gone again within a couple of days. It has some of the symptoms of ITB but not all of them, and stops above the knee so not related to the sciatic nerve / spinal stenosis which caused significant problems two years ago.
Basically, I can’t help other than say I have experienced similar, and survived.
I am heading for 74 around Xmas…
Good luck, and persevere…
Pete