I run Windows 7 and Office 2007 on my PC. Recently, I installed EaseUs sync on my PC and tried to configure it to sync to an external hard drive. After many attempts to get it to work properly including an extended tech support call with the company, I removed the program from my PC.
What I noticed happening was that saved files either started to revert back to earlier versions or they just disappeared.
I started doing research and came across a blog on technet in which they described the very circumstances I was encountering except they were either sharing files or were on a network and I am not.
First of all, the only way that a file can revert to a previous condition is if there was a saved copy of it somewhere (most likely an auto saved copy), and then something triggered the autosaver to restore the previous version.
Going to Office 365 might solve the issue (might not), but I think there are less drastic things that you can try first.
Change your default save location for Excel and Word to a folder that you aren't going to save any documents to.
Go everywhere that autosaving is being done, and turn it off. This includes EaseUS (you've already done that one), any autosync software which came with your external hard drive (e.g. Memeo), and Word or Excel autobackup. This will eliminate the possibility of Word or Excel having a previous version to restore.
If you have any kind of cloud access on your computer, make sure that the folders you save your Word or Excel documents in are not part of the cloud autosync.
Whenever you want to save a copy of a document, first choose Save-As, and manually select the folder to save the document, then save it. From that point on, you can choose Save.
If this fixes things, then I would try to set the default save location for Word and Excel to a folder you want to save to, and then see if the problem resurfaces. If it doesn't, then you're good to go. If it does, then change the default save location to something else, and manually choose where to do each save.
My Computer
At a glance
Linux Mint 18.2 xfce 64-bit (VMWare host) / W...Haswell4 GB
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Dell
OS
Linux Mint 18.2 xfce 64-bit (VMWare host) / Windows 8.1 Pro 32-bit (VMWare guest)
CPU
Haswell
Memory
4 GB
Monitor(s) Displays
Acer 23"
Screen Resolution
1920 x 1080
Hard Drives
Two hard drives, 1TB each: One for Linux, one for my data.
Keyboard
IBM Model M
Antivirus
Sophos (Linux), Trend Micro (Windows)
Browser
Firefox, Opera
Other Info
I use Samba to share my data drive with the other computers at my house and with my guest session in VMWare Workstation Player.