Gimbal lock may be?

[saadi-tech]

Hi, thank you for the good work. While working with Kalman filter for orientation, I have noticed that if the pitch value goes to 90 degrees, the angular measurements go crazy afterward. I can see many unwanted spikes in the readings after the pitch=90 condition. I think it is due to gimbal lock. Any thoughts? Please look at the roll and yaw after the suspected gimbal lock.