ISSUE:
The Steam Backup feature is creating inaccessible folders with certain Steam games. (Steam Backup creating a backup folder name ending with a ".")

OS:
Windows 10

STEPS:
(Example: FEAR, App ID 21090)
1. Select Library in Steam Client
2. Right-click on F.E.A.R. select “Manage”, then “Backup game files…”
3. In the popup that appears, browse to a location where to save the game backup
4. Click on “Create Backup”
5. Allow the backup to complete
6. Click on “Close”

RESULT:
1. Steam Backup creates an inaccessible folder due to the backup folder name ending in a "."
2. The backup cannot be restored, Steam Client cannot read the (inaccessible) backup folder
3. The (inaccessible) backup folder cannot be deleted using normal/standard methods
4. Attempting to move the inaccessible backup folder will result in a Windows error (Unspecified error: 0x80004005). May also lead to system crash/reboot and possibly hardware failure/damage depending on circumstances.
5. In my case, and how I first discovered the issue, I was moving folders on my external HDD. When I moved the folder containing all my Steam game backups, my system crashed and rebooted to BIOS/UEFI. Upon reboot, I moved each game individually, one at a time. When attempting to move the “F.E.A.R.” backup folder my system crashed yet again. Luckily, there appears to be no damage to my external HDD. I viewed the external HDDs S.M.A.R.T parameters to check for errors/faults/damage. No faults (so far).

Further Info (1): Checking the backup folder properties, the folder size will be reported as 0 Bytes. Under the security tab, the message “The requested security information is either unavailable or can’t be displayed” will be shown.

Further Info (2): I noticed in the app manifest file (Location: Steam\steamapps\ appmanifest_21090.acf) there is a line in the script, "name" "F.E.A.R." Presumably this is what Steam Backup uses to provide the name for the (inaccessible) backup folder. Two lines further down in the app manifest script is the line "installdir" and the game folder name. This folder name is a far better option for Steam Backup to use as a backup folder name.

Further Info (3): There are various methods of removing a folder whose name ends with a "." I have not provided/suggested a method. I believe Steam should provide what Steam considers the appropriate method of deleting such folders, or provide a tool.

The results will always be the same when Steam Backup creates an inaccessible folder (a folder name ending with a ".") I do not know how many Steam games this affects, I do not have access to every Steam game or App Manifest. Whatever the game, if the backup folder name ends with "." then same issues will be present and the results will be the same.

It is well known that Windows will not accept folder names that end with a "." Steam Backup creating inaccessible folder names ending in a "." is a novice/rookie error and should be easily fixed/corrected. If I had known about this rookie error, I would never have used Steam backup in the first place.

I will no longer use Steam Backup. Disk imaging is far quicker and obviously far more reliable.

On a side note (For anyone who still use Steam Backup): For those who have Steam Workshop items, it would handy to have a method of backing these items up. I normally have 80 to 100 GB of workshop items and sometimes up to 200GBs, there will be those who a have a lot more. Having to redownload 100s of GBs would be really annoying. A way to backup workshop items, much better idea. For example, when backing up (for example) Arma 3, the Arma 3 workshop items are also included in the backup.