After setting ARSPD-USE to 1, the aircraft experiences oscillation

I am testing a 2.4-meter aerial survey aircraft. Equipped with Matek’s airspeed meter. The altitude control with ARSPD-USE=0 has been adjusted and can now fly normally. For better flight, I hope to control the throttle using an airspeed meter: ARSPD-USE=1. But after modifying the parameter, I entered cruise mode and found that the aircraft was very unstable with wavy lines in altitude. And the automatic throttle fluctuates greatly, making it almost impossible to fly. Please help me see what the problem is.

I switched to cruise mode twice between 34:20 seconds and 35:14 seconds in the log, and the issue was discovered here.