Same issues here, and searched in google lead to this page.

here is more information:

I am running code like this:

python
                            for kfp in fcurve.keyframe_points:
                                if kfp.co.x >= startFrame and kfp.co.x <= endFrame:
                                    print("kfp.co.x: " + str(kfp.co.x))
                                    fcurve.keyframe_points.remove(kfp)

There are 2 problems about the running result, to me, looks like 2 bugs, not one.

For example, if I have camera keyframes at frame number: 1, 30, 31, 60, 61, 90,91, 120
And the start and end frame number is: 1~250

Then, the loop above, will only print keyframe at: 1.0, 31.0, 61.0, 91.0.

Get it? If there are 2 keyframes, one next the other, the first keyframe is never handled.

And since the last keyframe is at frame 120 and there is no next keyframe at frame number 121, it gives me the error:
RuntimeError: Error: Keyframe not in F-Curve

So, since it alway leaves half keyframes un-removed, I have to run that script about 5~6 times to remove all the keyframe in a range.

btw, this issue can be confirmed in Blender 3.0 too.

so the workaround is to use a loop that checks the length of the array until it is empty I guess

This is not a valid bug. This is a common programming problem where you cannot remove items from a list from within a loop using a forward iterator because the iterator is invalidated after the first removal. There are a number of ways to fix this, but the easiest way is to just reversing the iteration order (e.g., reversed(fc.keyframe_points.values())).

In T96488#1379206, @Colin Basnett (cmbasnett) wrote:

This is not a valid bug. This is a common programming problem where you cannot remove items from a list from within a loop using a forward iterator because the iterator is invalidated after the first removal. There are a number of ways to fix this, but the easiest way is to just reversing the iteration order (e.g., reversed(fc.keyframe_points.values())).

Agree that it's just a common programming problem, good point.