Game keeps resetting texture memory option to "Medium" or "Low

[Arkvold]

For some reason, when I set the "Texture Memory" option in my in-game options to "High," it doesn't stick.  It gets reset periodically to Medium or usually Low.  My system can easily handle the High setting with no loss of FPS save in the most visually-cluttered situations (like multiple nullifiers coming out of a 90% void rift while three teammates are all spamming powers), so I'm not sure why this is occurring.