The OSD doesn't work when flight(1-5 minutes) on Pi4B ground

Hi,
I have two questions:

  1. The OSD doesn’t work when flight(1-5 minutes) on Pi4B ground.
    Then, the screen repeatedly displays “Starting mavlink telemetry uplink”.
    But on the same time Pi3B+ OSD is work.

  2. The OSD flight speed is wrong.
    The display speed is about 2.5~3 times as fast as the actual speed.

Please help.

ground:
Pi4B 2.0.0rc6~rc11
ASUS USB-AC561、Taobao Card1

Pi3B+ Nightly 2020-4-13
ASUS USB-AC561、Taobao Card1

air:
test 1:
Pi3A+ 2.0.0rc6~rc11
ASUS USB-AC56*1

test 2:
Pi3A+ 2.0.0rc6~rc11
ASUS Taobao Card*1

FC:
U6 Flight Controller

The OSD itself and downlink telemetry are working, the message is about uplink from ground->air (which you’re likely not using). Probably a settings file problem though, can you upload openhd-settings-1.txt from the ground SD card?

The speed I can look in to, home distance might be caused by the flight controller not providing home position, does that flight controller run ardupilot or another firmware?

Hi,
Sorry, my English is not good.
When I was doing a flight test, the two ground of pi3B+ and pi4B were turned on at the same time and the same aircraft.
The OSD on the pi4B ground was work at the beginning,but after 1-5 minutes it wasn’t work, then screen repeatedly displays “Starting mavlink telemetry uplink”.
At the same time ,the pi3B+ ground OSD is still work.
In addition, the pi3B+ and pi4B OSD display flight speed is about triple as fast as the actual speed.

I use U6 flight controller, it supports mavlink
https://www.amazon.ca/Accessories-Controller-M8N-GPS-Current-Airplane/dp/B07RR2YWLK

Attached is the openhd-settings-1.txt of my pi3B+ and pi4B ground.
pi3b+
pi4B