Agreed. That's another problem you should get figured out. Probably pretty easy. There is a little electrical connector at the bottom of the tank (bottom, rear, driver's side) with two thin wires going to it. It could be that leaked coolant residue is interfering with the connection there at the plug/socket. First thing to do is to unplug, clean, etc.

And of course, if the sensor is saying one thing and the floating rod is saying another, believe the floating rod.

If the problem is not at the connection, that magnetic float sensor has been known to be flaky (or even non-existent) for some non-BMW brands.

BTW, if you do end up having an issue with your sensor (i.e., not the connector, your tank is good, etc.), this thread has a ton of info on it. Pics of it cut open, etc. so you can see what that float looks like, the connector location, etc. After all the mysteries about its workings are discussed, the answer is given (I think) in post #16.
https://xoutpost.com/bmw-sav-forums/...l-message.html

But the sensor problem is separate from the leaking coolant problem - solve them both.

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2001 X5 3.0i, 203k miles, AT, owned since 2014