I never used UKismetMathLibrary::RInterpTo, but it might be that it is not meant to be used every frame. I use something this instead:
float Speed = CLAMP(DeltaTime * LerpRotationSpeed, 0, 1);
FQuat CurrentRotation = Camera->GetRelativeTransform().GetRotation();
FQuat NewRotation = FQuat::FastLerp(CurrentRotation, TargetRotation, Speed);
Camera->SetRelativeRotation(NewRotation);
The CLAMP function is a micro I use to make sure the value doesn’t go above 1 on low framerates:
#define CLAMP(value, min, max) (value >= max ? max : value <= min ? min : value)
I hope this helps