Rate Stretch + Optical Flow issue ONLY at out point

I'm slowing a clip down considerably, to 26%, then interpolating with optical flow. Looks great, very smooth, no artifacts after rendering preview.

However, no matter how long or short I make the clip, just before the final frame 3-4 frames are freezing (or duplicating, basically a frame hold for a few frames) and then it resumes on what would be the correct final clip frame if it hadn't froze (in other words, I can't just trim out the freeze, the frames are skipped anyway).

These frames are all there before I render and the hold issue always occurs just before the end of the clip no matter where I choose to end it.

I'm frustrated because I finally got the slow motion to look perfect for a looping graphic and now it jitters right at the loop point so it's not seamless.

I've tried changing the speed but it doesn't look as good, and tried interpolating with Frame Blending but it also doesn't look as good.

26% with Optical Flow creates EXACTLY the look I want, but there's this weird frame issue that's otherwise ruining the loop.

Anyone ever had this problem? I know optical flow isn't usually ideal when slowing a clip down this much, but it's working so beautifully up to those last few frames. I need them only because it's a looping file.