Plane ekf origin alt error

With arming_REQUIRE=0, and in the absence of a compass and airspeed sensor, why does ORGN_ALT change to 702 m during initialization? This leads to a negative altitude reading upon ekf3_active engagement after liftoff, causing the aircraft to dive.
Though this error happens infrequently, I must maintain arming_REQUIRE=0. Is there any solution available?

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