MP rangefinders on tuning window

This is a capture of a rangefinders static test:

  • RangeFinder1 points down. Its indication on the tuning window (red trace 40cm) is correct.
  • RangeFinder2 points to the front. Its indication on the radar window (1m) is correct, but on the tuning window (blue trace) measurement is 0.
  • RangeFinder3 is not enabled and not mounted (is this indicated by all lower case letters on the tuning window?).

What can happen with RangeFinder2 measurement 0 on the tuning window?

MP 1.3.77 build 1.3.8143.23443.