Not Receiving Mission/Command ACKs

Currently running Copter 4.0.3

I am communicating via MavLINK and having an issue where I never receive an ACK sporadically. I have a Jetson Nano connected via serial directly to the TELEM1 port on the Pixhawk. The two areas where I am seeing this is when I send a MissionClearAll and a CommandLong(MAV_CMD_DO_SET_MODE).

First the Clear All case: I am preparing to send a new mission and first am going to clear out the old mission. Generally this works and I will receive a MissionAck shortly after sending the MissionClearAll, however sometimes I will never receive the ACK. I do see, however, that shortly after the current mission is cleared from whatever it was to 0 which leads me to believe the Clear All was successful.

Next the Set Mode case: I am trying to switch the autopilot mode (does not matter if going to AUTO, BRAKE, LAND, etc) and am sending the CommandLong(MAV_CMD_DO_SET_MODE). Again, generally this works, however sometimes I never receive the CommandAck. Despite this, I can see that the autopilot mode actually changes to the requested mode.

I am not sure if this is a bug or if I am somehow missing the ACKs. Either way, I can develop a workaround by also listening for mode changes and current mission changes in case the ACK is missed.

If an ACK is missed, repeat the command! That is the protocol.

Right, but I shouldn’t be missing ACKs ~30% of the time when I am hard wired to the autopilot right?

I am not 100% sure about this but could you please try to reduce the stream rate of another telemetry, which reduce the SR1_X to lower values.