RPLidar A3 problem

maybe someone has an idea. The A3 needs 256k boud. It seems to me that when I activate it, the Cube Black is overloaded. This manifests itself as “Sensor Lost” messages from Horus FrSky S-Port Passthrough Telemetry. When I deactivate the lidar, the telemetry works without sensor loss.

Hardware and software:
CubeBlack hexacopter with Arducopter 3.6.12

Serial 1: 433Mhz radio (57600)
Serial 2: FrSky S-Port Passthrough
Serial 3: Here2
Serial 4: Lightware SF11 Lidar (115600)
Serial 5: RPLidar A3 (256k)
SBus out is on (50Hz)

after arming the telemetry stops working immediately

I am grateful for every hint!