This is gonna sound stupid but my friend had a similar problem. he was complaining that he had a very hard time turning the bike in one direction. And the handlebars wanted to pull to one side. He also said that he thought I hooked up the brake cables wrong. He was not a tech person in the least.

The problem was that he accidentally spun the handlebars around 360 degrees so that his brake cables were wrapped around the stem. Caused all sorts of weirdness. Flipped the handlebars back around the other way and all was well with the world.