I recently (March 17th) uploaded 3 files to append tags to our customers.
Come to find out instead of appending the new tags to their accounts, the account was not only wiped of the old tags, it was also wiped of the email history.
I looked at some of the emails I know had tags on them prior and have received emails, such as my own and my wife's.
Working with support, they are telling me there is no way to restore my DB from a period in time, was asking for it to be restored at 12 noon - 2 hours before my upload, NOR do they backup or save changes to Tags in their dataset.
Basically I am here with at least 1100 emails missing at least 1 other tag, many at least 4 and I have been asked if I know what they were prior?......
This is honestly very scary in this world of backups and data. Make sure you have your own backups done all.