Well, better late than never but found what was causing this a few years ago.

I mentioned this to a tech at a shop during unrelated work and it just so happened he has seen this before.

He said the bottom of the fuel tank has a small depression/divot that the bottom of the float assembly is designed to sit in

If the float assembly is not seated exactly there it shifts and this happens.

I had them install a new float right then and there and it is fine to this day.

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04 X5 3.0i auto
03 X5 4.6is