Jerky Playback when I increase speed of Red footage in FCP?!!

Hey friends

So iam still working on this 2k 24 fps RED project which I posted about last week in regards to the banding issues.

The latest issue I have is that whenever i apply a speed change by increasing the clip anywhere from 10% to 100% above its actual speed I get stuttery playback - or maybe jerky playback is a better way to describe it. I have tried it on all of the clips and it happens to every single one no matter how small the speed increase is - wtf?!

I the footage was originally shot 2k at 24fps and then i transcoded it to 1920x1080 in RedRushes for editing purposes...this time around i did not convert to 23.98 because its for web only at this point and I am ok with just viewing it in fcp and not on a crt or hd monitor.

any thoughts on why this might be happening??

thanks

Lisa