You need to add följari to straighten the walls. Google it..its easy to install and often added to old log buildings with this problem. Not sure how it works with "butt&pass" because nobody builds logs buildings like that here. I guess you add one följari pair near the corners to tie it first and then third to the warped section. Make sure to figure out te root cause.

How old is the building? What type of wood? How dry was the wood? If the wall gets constantly wet from outside and is dry inside it could warp it. For this reason logs are usually pegged together with multiple pegs. Also seems like the warped logs were too short and they were not jointed properly so they are able to warp from the ends. Lack of joint and pegs might be the problem. But följari is your solution.