NOVA 2400 H2 engine cant shut down

Hy Guys,
We have NOVA 2400 H2 engine Drone H6.

We have problem with the engine not turning off automatically, so we had to turn it off by pressing the emergency stop button.

From running (rpm 12 - 13000) to idle (rpm 5-6000) everything is normal, but from idle position engine won’t turn off
Please give us feedback and more information to solve this problem.