Issue with reverse frames - Animate

Hoping someone can point out where I'm goinging wrong...

I am trying to reverse frames in animate and have done successfully many times. However, when trying to reverse frames this particular time, instead of reversing the frames it put everything into one frame. I'm not sure why it's doing that?

I'm highlighting the frames I want to reverse, right clicking, and then selecting 'reverse frames'

Any ideas?

Many thanks!