zoom in works but zoom out doesn't work - no transition

Hi (I'm newbie)

nice to meet you and hope i get some help

I'm zooming in and out on the same clip. no transition, just the same clip. the zoom out doesn't work

I put 4 keyframe since i need to keep do a quick zoom in, then keep the the same zoom factor for some time and then go back to the original, so something like:
100% 150% 150% 100%

It seems the last keyframe is ignored. the same happens to position. while speed changes are working perfectly.

here you can see the 3rd keyframe number: scale is 150%

and here in the 4th keyframe the scale is 100% nonetheless the video scale remains 150%

you can compare to the 1st keyframe at 100%

Any idea? Thank you very much