I have set the dark theme on both Invest and CFD. When I switch form CFD to Invest the theme switches from dark to light randomly once in a while. About once a week I guess.
There was another topic about it, but can’t find it
Hey there 
The reasons for the problem you’ve described could be quite many, the vast majority of which are not related to, nor can be influenced directly by Trading212.
Nonetheless, the best course of action would be for you to :
- Try from a different device/ web application
- Clear your cache & cookies
- Restart the device & app
If those do not work, please approach me directly so that we can see what else we can do on our end 
i see it everytime my browser’s cache is cleared. on my personal laptop where i religiously clear cookies and cache every night before shut down, this happens, but on my work laptop where i have no control and i’m more than certain that the cache doesn’t get cleared on restart, it doesn’t happen. not sure if that helps.