Let's see, the Landa probe is a sensor. If it gives you mistakes what can be ???
You have to ask yourself, that it is failing so that the Landa value is altered.
If the code gives you a Landa failure it does not mean that the Landa is broken, but the (CO) or (oxygen) are uneven.
Look at the EGR, which does not find cracks where the air can enter the exhaust or admission collector, that the injectors are spraying and does not drop into the cylinder, which is burning oil by a joint that gives way to the engine.
way to know better you put an exhaust gase meter if the meter fails, because you know is not the Landa.
And if the meter gives you well then check the cables or look if it carries 2 las.