Server Version#: 1.25.5.5492
Player Version#: 1.40.1.2823-6f60f3a7 and 1.31.0.2254-43df1e6e1
Note: I do have the Plex player installed in a non-default location on a different drive.
When I launch the Plex player it reverts to version 1.31 from whatever version it had updated to.
The time I launch the player after that it prompts for an update and launches the updated version. This updated version lasts until I relaunch the Plex player.
As a note, when I inspect the updated instance of the plex player it appears to be installed the default installation location, NOT the location I installed the Plex player in. It has installed there instead of updating my existing installation.
It seems you have two installations of Plex for Windows.
Fully remove it from your system, then re-install to the desired location.
In Control Panel → Programs and Features, uninstall Plex for Windows.
Remove it from any other location on your system. Just drag the folder to the trash (the default installation location is C:\Program Files\Plex\Plex).
Delete the Plex for Windows data folder, %LOCALAPPDATA%\Plex (see Intro & Install docs linked above).
If you’ve other Plex apps on the PC make sure you do not remove their data directory (Plex Media Server data directory location).
Reboot your PC.
Download the current version of Plex for Windows and install in the desired location.
But, Plex prompted for an update when I launched it today, and it installed the updated version in the default location, not the expected result of my non-default install location.
Now I have the same issue as before, with a non-updated version in the location I want, with an up-to-date version in the location I don’t want.
Why can’t it just update where I had it installed?
Here is a workaround that will help. It stops Plex for Windows from auto-updating. When an update is available, you can download and install manually, selecting your non-default install location. To be notified of an update, subscribe to the Plex for Windows announcement thread. Scroll to the bottom of the thread and change Normal to Watching.
If I might ask, why install in a non-default location? The application does not require much space (420 MB on my system). Downloaded media are placed in a different location, %LOCALAPPDATA%\Plex\Plex Media Server\Sync. That location cannot be changed within the app, but you can move it by using a symlink (reference).