When you edit a keyframe, you can select the interpolator for that keyframe, and if that interpolator is Catmull Rom, you can also set an alpha value which is how smooth the curves are. If you set it to 0, it acts like linear interpolation; straight lines and sharp cuts. If you set it to 1, it looks more similar to the Cubic interpolator, where the motion is extremely smooth but can take detours sometimes. The default value is 0.5, I recommend tinkering with that value a bit to get the smoothness you want.
Another trick is to move the position keyframes in time a bit. Usually weird camera paths are caused by sudden changes in velocity, so spacing them out often helps. I recommend enabling the path preview using H, then flying away a bit so you can see the full camera path, and then move around some keyframes in time until the path between them looks good.
If that still does not help, slicedlime has a great video series about mastering the Replay Mod, and in episode 1 he talks about these types of issues.