No clue what to tell you! What's your computer hardware, OS & AE version... precise version numbers, please.
Well, maybe there's something you can do right now -- transcode the problem clip to a good intermediate codec. That 4K stuff doubtlessly has the bejeezus compressed out of it, which can really screw things up. If it works then, you know what to do. Just be prepared for some REALLY big file sizes after you transcode!
Proteus IV 32GB RAM, 512GB SSD, 8GB Geforce GTX1060 graphics
Windows 10 home
latest adobe premiere version (v2018)
If you have not already done so, please update After Effects. You should be clear of this issue after doing so.