I had the same problem and deleted my settings folder for that toon, worked like a charm. I now keep backups of the last two settings folders so I can repair the folder if needed.
I am convinced that the when the bot writes to the settings file it may become corrupted if another process is using the file. I have that problem when exiting multiple bots too soon.
But try deleting the setting for that toon. Try logging onto another toon on same account and if it goes through then the settings will probably fix it ... or not. I am like Edison who tried a lot of materials to get the electric light done.
'I have not failed. I've just found 10000 ways that won't work.'