I'm mostly unable to select the boat in the Underdark using a controller on Stadia. Video below. It's fine with mouse + keyboard. (Stadia with controller bug.)
https://youtu.be/oY70FEd2QQAI believe the selection/interaction area is too small/narrow. When playing with the controller, there's only a finite number of directions that your character can face, it always seems to snap to one of those rather than obey the controller and stay put.
This selection wonkiness occurs when looting and interacting with other things sometimes as well.
FYI another workaround for some objects is pressing R3 (right stick) to move a targeting cursor rather than using character movement for selection.