Redux not remembering settings

This is on Windows 10. Reaper 6.58.

It seems that on my install the settings file isoveridden on exiting the DAW for some reason.

When I change a setting, e.g. the scaling I can see it changing on Config.xml, e.g.

<UIScaleFactor>150%</UIScaleFactor>

Then I leave the code editor open and close Reaper and it becomes this:

<UIScaleFactor>Auto</UIScaleFactor>

Notice that if I only disable and then enable the plugin it is fine. It only happens on exiting Reaper (when unloading the DLL I guess).

It happens with every setting. I can only use defaults. What to look for? Is this a bug or something with my install?