Thanks for the suggestions.

• I tried disabling steam input but it appears you can’t do that for the Steamdeck controller. It says “Always enabled” next to Steamdeck controller.
• I tried binding the walk key to a back button as well, but the back buttons aren’t recognised by the game at all. Possibly another hint that the game is having issues with the Steamdeck controls.
• I did adjust the deadzone in the Steamdeck controller config. The game itself only has sliders for aiming not walking.
• That’s a good shout. I had a quick look at profiles too but didn’t see anything that might fix the issue. I will look a bit more. As a last resort I might have to make my own keyboard based input though not sure how well mouse aiming will map to the sticks. It’s just a bit annoying I have to do this at all.