50 fps isn't smooth when I change the speed to 50%

[#1]

I have footage in 50fps, and when the clip is on the 25fps timeline - I want to get a slow mo effect so I change it to 50%, and it's comes through choppy - as if I had put 50% on a 25fps clip.

The footage is all 50fps. The timeline is 25fps. I have other footage on the same timeline using the same camera that I made 50% speed and it looks smooth just as it usually does.

Any ideas, much appreciated! 🙂

[#2]

I have footage in 50fps, and when the clip is on the 25fps timeline - I want to get a slow mo effect so I change it to 50%, and it's comes through choppy - as if I had put 50% on a 25fps clip.

The footage is all 50fps. The timeline is 25fps. I have other footage on the same timeline using the same camera that I made 50% speed and it looks smooth just as it usually does.

Any ideas, much appreciated! 🙂

[#3]

have you tried "optical flow" in the frame blending options ( I think that's what it's called - not at my edit system at the moment).  Will need rendering

[#4]

For such type conversions (50fps to 25, or 60 to 30) I'd use option "interpret footage", that guarantee smoothness (assuming your shutter speed was 180deg or so). But, you may try alternative approach: https://youtu.be/LDO9RIA_g2Y