Currently an issue exsists with the API call "setUserv2", at this time the issue has been raised to our development team for investigation. I would advise that you use the "setUser" API call in the meantime to make changes to existing technicians without error.
I will be sending you a direct private message to obtain the email addresses of any effected users, I will send this to my team for correction, once corrected the emails will be avaialble for use within an account once again.
The issue in the API call makes reverting changes fail, this is currently under investigation. As mentioned I'd advise using the previous available API call for these changes. The RPAT addon has been depreciated, thus you can use the v1 version of "setUser" to make these changes without error.
More info on that call can be found at the following URL: