Anthony,
There are two Revit.ini files, a user Revit.ini, in the User App Data path, and there is a Revit.ini in the UserDataCache folder in ProgramData. When you edit the options you are editing the user copy, but some things (like paps) are enforced from the UDC version (if both have the same Install GUID). The trashed histories is not something I have seen before, and in theory the UDC version shouldn't not have any info in the recent files history, so if anything a UDC overwrite should be deleting all the recent files. But perhaps the UDC copy has something there?

Gordon

Thank you for your reply, Gordon.

I am aware of the two Revit.ini files and update the local UDC version with our office standard during installation.

I don't know what "paps" are, nor have I ever understood the function or necessity of the InstallGUID parameter. It currently is in our UDC version and consequently in all our AppData files. Should it be there?

There are no File History lines in our UDC Revit.ini.

I am trying to establish a pattern as to when this issue happens and what I think is happening is that:
* When I make a change to the Options > File Locations > Places listing my file history is diminished or deleted (on the next startup).
* If I set a new library location on the network then the path is respected on the next session.
* But if I set a new library location on my local C drive, then it is changed to a network location the next time I come in.
* I can't see any evidence that the UDC file is being copied down - but I might be wrong.