Missfiring Steep Hills backing up

Hi, glad to join you all.
just bought a Can Am Otlander 450 Max with 5 hours on it. Today i had to back up on a steep hill with a passenger on board and the engine started to misfire. I did the reverse operation on level groun and was ok. The tank was almost full. Later, i tried the same steep hill backing up alone and misfired again.
What could be? Regards,
Marcos, Rio, Brazil

Missfiring Steep Hills backing up

Hi, glad to join you all.
just bought a Can Am Otlander 450 Max with 5 hours on it. Today i had to back up on a steep hill with a passenger on board and the engine started to misfire. I did the reverse operation on level groun and was ok. The tank was almost full. Later, i tried the same steep hill backing up alone and misfired again.
What could be? Regards,
Marcos, Rio, Brazil