When I try to add a keyframe with "I" in the curve editor or the dope sheet while there is no change since the last keyframe (to make the bounces with the z-axis for example), it just moves the previous keyframe to the location of the cursor instead of creating a new keyframe. This occurs whether I choose "All Channels" or "Only Selected Channels" and whether Automatic keyframe is enabled or not. It makes it more tedious to animate the bounces because I have to change the z value to be able to add a new keyframe, before resetting it to 0.
Any help would be appreciated :)
For my problem it was in fact "Only Insert Needed" that must be unchecked. I guess when the value does not change they suppose we don't "need" an additionnal keyframe.
Thank you very much for the help !
And by the way, thank you for all the time you invest in the community, you manage to answer all the questions and comment in details all the exercises, this is very helpful for us, students :)