Super 8 project accidentally filmed at both 18fps and 24fps

[graveybaby]

A Super 8 project was recently captured on a Canon Pro814, on multiple cartridges all filmed and scanned in at 24fps (or so I thought). When I received the footage I realized a few cartridges were accidentally filmed at 18fps and now look too fast! I can't figure out how to make it all match...

The footage came back in two large ProRes 422 HQ files. If I try to slow down the few clips filmed at 18fps in FCP it looks jittery compared to the other footage. From my limited knowledge and research it looks like I may need to duplicate frames to make everything look smooth and match, but I'm unsure how. I read that the Neat Video plugin may be able to do it but my attempt wasn't successful. I'm willing to pay for a service or buy a plugin - whatever can get this fixed so I can deliver to the client. Any guidance is appreciated for this newbie!

[davexnet]

It seems as if the 18fps-scanned-at-24fps needs to be slowed down to 18fps then through interpolation, frame duplication or similar,
brought back to 24fps.
Easy to do in an Avisynth script; maybe doable in the NLE directly, but will need somebody further to confirm

[clashradio]

Last month I had some Reg 8 and Super 8 scanned at 4K, 24.000fps (not 23.976). I use Vegas Pro and adjust the play back rate accordingly. For Reg 8 (filmed at 16fps ) I slow the play back rate to 0.667. For Super 8 (filmed at 18) I set the rate to 0.750. These are all in a project of 23.976 for BD delivery.