Theme keeps resetting when I reopen the browser?

[FromASloth]

So I had theme Sonical from the time I joined until around November, when the theme Seasonal Sonic released. I switched over to Seasonal Sonic for the holidays, and kept it until about last week. With the holidays over I'm trying to switch back to Sonical, but every time I reopen the browser (whether it's because I turned on my computer or simply closing Safari), it goes back to Sonical.

 

Is there a way to maybe fix it, or am I stuck?

[SIXTH-RATE SOMA]

Are you using or switching between mobile devices, per chance?

[FromASloth]

I am, actually. I usually use SSMB on my phone while on the street.