Unplayable on a SteamDeck once you get to the Monos

[512GB OLED]
It does not matter how low I drop the graphics settings ( i.e. 600x400 Medium) as soon as I enter a Mono FPS will drop to near zero and I will be forced to quit to the desktop because the system is effectively unresponsive. Playing through the campaign I definitely had times where I had to ‘reboot’ the game to make it through a section. But with the Monoliths it is a complete failure. Cannot play at all.