Using quaternions to rotate an object (OpenGl,c++)

I started to learn quaternions and got very weak idea of how they work. So I blindly followed some tutorials on you tube on how to rotate object with glm.
I had problem with weird rotations when I used Euler angles once I switched to Quaternions rotation was normal, but now rotation gets fuzzy in terms that it changes speed, when it should be constant.

glm::vec3* rotationAngles = modelVertex->getRotation();

glm::mat4 translate = glm::translate(glm::mat4(1.0f), *modelVertex->getPosition());

glm::mat4 mQuat = glm::mat4_cast(glm::normalize(glm::angleAxis(glm::radians(rotationAngles->x), glm::vec3(1.0, 1.0f, 0))));

return this->perspective *translate * mQuat;

rotationAngles->x is constantly increasing by some constant (20 degrees)

In my loop I have code that goes angle+=20; and then rotation.setXAngle(angle);

Funny thing is this only happens when I’m using rotation on both x-axis and y-axis, when for example I only rotate on x-axis,speed does not change.