I am having similar issues and was visiting with my sister who is not a dentist but is a PA. She also had some similar issues and after 2 root canals, it was determined that she had an atypical root (3rd root) that only 5% of the population has…it hadn’t ever showed up on X-rays and the dentist discovered it during the 3rd root canal..it solved her issue. Hope this helps someone. Also, it can be hereditary to have the atypical root.