Steps to reproduce:
- open page in NWE
- make changes
- open Publish dialog, click Show preview (probably not really necessary but this is how I got to the error)
- wait a few minutes
- click Review your changes
Will result in a badtoken error message, which gets cached in memory as if it were the change info (so closing and reopening the publish dialog will just redisplay the error without any attempt to repeat the request).