however, doesn't seem to work anymore. teacher module keeps messing up on tradeskills, and class training.
1. Don't post a mile-long list of all of your addons. You can very easily see if the problem is related to another addon by logging in with all other addons disabled. If the problem still occurs, it's not related to another addon, and you don't need to post the list. If the problem goes away, then you should enable your other addons one by one until the problem reappears, and then post only the name of the last addon you enabled to cause the problem. Nobody wants to scroll through a huge list that's probably not relevant anyway.
2. Given that the topic hasn't been updated in nearly a year, and the addon hasn't been updated in nearly a year, it's probably safe to assume that it's no longer maintained, developed, or supported. Although I'm not familiar with the trainer API, the error message you posted seems to indicate that it's changed since the addon was written, meaning the addon needs an update in order to function. At this point I would say just uninstall it.