Game does not show my resolution under resolution settings

[Kozi]

I have a 2560x1080 monitor and if I select "Use Custom Resolution", then 21:9, the game only shows one low resolution option.
After choosing the resolution, "Use Native Resolution" stops working and resets itself to "Use Custom Resolution" every time I leave and come back to the settings menu.

 

[jet.heferen]

Seconded. If I select 21:9, I only get 1834x786 on borderless, and fullscreen only gives me "#dota_settings_no_mode_resolution" as an option.