Edited proxy becomes laggy

I have a video file that I automatically turn to proxy. After that I split a part of it and changed it’s speed to 10x. Now during playback this sped up part is laggy despite still being tagged as proxy. I cannot find any option to re-proxy this bit to make it run properly. Is it an expected behavior in Shotcut or is there something wrong with my workflow? Should I do the splits in video before I create a proxy?

Maybe your computer does not have high enough performance to play the proxy file in 10x fast forward.

Here is a suggestion to try:

  1. Save your project and close it
  2. Open the file that you want to use at 10x speed
  3. Set the speed to 10x on the clip
  4. Export
  5. Open the project you saved and open the 10x clip that you just exported

What is the resolution of the proxy (see Properties)? Ensure that the chosen resolution option in Settings > Preview Scaling matches that. Otherwise, it must scale each frame (after seeking and decoding it) from proxy resolution to the resolution of Preview Scaling (or Video Mode if None).