Mission mode in GPS denied environment


I’m trying to fly an auto-mission on PX4 Firmware in GPS-denied environment using a 3D position estimation from onboard camera and EKF2. When I try to start a mission, I get an error saying “Unable to start a mission. Vehicle not ready.”. After going through bunch of discussion regarding the topic, I understood that the mission mode does not support local frames and I have to use fake GPS to provide estimate in global coordinates.

In QGC, I can see the global position of the UAV mirroring the changes in the local estimation, the UAV gets a GPS lock at expected position, and the UAV is able to auto takeoff and hold its position. However, after I try to start a mission, the same error occurs.

Does anyone have an idea why this happens, or if it is possible to fly in MISSION mode using the faked GPS estimate based on the local vision position estimate? Or am I forced to implement to fly in OFFBOARD mode?

Thanks for replies!