Lost "Notes" - help!

Do I need to do anything to maintain the CRM?
I installed and configured our version about 2 years ago.
Aside from setting up semi-weekly backups I pretty much left it alone after that.
We have ~10 staff using it and about ~30K Contacts in it.
The version is Version 7.9.7
Now our staff tell me some of the “Notes” (Contact/History/Notes) have gone missing, as well as some content from various fields for several “Contacts”.

Is there anything I can do to find/restore lost content?
Is there anything I should be doing maintenance wise to prevent any future losses?

Thanks!
Greg

If the entire instance is working great but Notes data are missing so you can consider table corruption.
If you have root access to that database you can mysqlcheck the tables notes and notes_cstm, eventually you can mysqlcheck all database’s table to make sure what is wrong.

Kind regards