That appears to have done the trick, thank you very much.
Although, r_customaspect doesn't appear to be a valid option.
Ah ok sorry I took that from my config, it's perhaps not a valid option anymore with the latest OA updates.
If you want more infos about why it did that: the game engine forcefully resize your desktop resolution when in fullscreen mode to adapt to the ingame resolution. That's at this moment that your icons get resized. Then when you quit the game, you get back your old resolution, but the icons were already moved away.
Normally, recent desktop managers have some protections against that, or you can find some third party tools.
Keep in mind that this problem may happens with other games (more specifically old games that force desktop resolution resize when in fullscreen), so you should maybe update your desktop manager or find such a tool to do the job, or just be careful to set the same resolution as your desktop in every game.