[Auste Liegute]

Hello, thank You for very informative videos about anesthesia! I use cold test before placing a cofferdam for composite fillings. But I have an issue with lower molars. I have patients that receive first aid somewhere else (for example pulpitis) and come to me to do the root canal treatment. I administer Alveolar nerve block, then infiltration near the tooth, that I am planning to treat, and also periodontal ligament block at 3-6 points around the tooth.
When I start the treatment usually there is no pain, some canals also are also painless and I can proceed till the apex and even through it. But there can be one canal that is painful for touching somewhere inside the canal, where I cannot reach with syringe needle. After I remove the pulp tissue from the canal, I can go through the canal and there is no pain even periapically.
I use Articaine with Adrenaline around 3 ampules.
Maybe You have any thoughts, where I make mistakes?