Could it be not you and the new olive then? Some other reason causing it to leak for years.
looked like it had been leaking from tap connector down both pipes and I cut it lower down but you never know. in between cleaning it i stuck a torch behind there and filmed it with my phone from behind it and then watched video back to see if it was clean enough yet. so could easily be a bit that isn't perfectly straight / round and i wouldn't be able to tell.
bath taps can be a massive pain.