According to them, it has not been fixed. They have a workaround that relies on your having a backup. They do not know what caused the problem.
From this thread:
We still have not located the root cause of this effect but firmly believe that it is caused by an issue in earlier versions of DEVONthink To Go 2.
- Identify the corrupted documents and try to replace them from your backup, best on a Mac or on another iOS device not affected.
And here’s a very long thread discussing the problem.
Due to this reminder of data loss, today I moved all my data out of DT, deleted all databases, and set up a DT_safe_store folder. Into that folder, I have ChronoSync do an hourly one-way copy of data from my working folders. I then created a new database that only indexes the data within those folders. This allows me to continue to use DT’s “See Also” function, without it having access to my working data.