Lidar Rangefinder does not work on Serial 5

Setup:

Auav X2
AC 3.5.5 (latest stable)
Lightware LW 20 connected to Serial 5 (Uart7)
11500 Baud

Lidar works on Serial 1 and 2 but not at port Serial 5.
Mavlink (57000 Baud) does function on port Serial 5.

Maybe it’s just hardware limitation?