Thanks for stopping by the Premiere forums and giving us that screenshot. To better help troubleshoot, could we get more details below, like what sort of spacer effect you might be using along with your specs.
Premiere Version: What is the exact Premiere version and build you’re using? Help > About Premiere or Premiere > About Premiere.
Setup/OS: Please specify Windows 11/10 or Mac, plus what macOS, along with driver version/build.
GPU Driver version/build(Windows only): We recommend updating to the most recent version; for NVIDIA users, we strongly recommend the Studio version of the driver.
Mac Chip (Mac Only): what M-series chip? If Intel, please include GPU.
Media Files: video, images, etc. and what types (can check under Media Properties)
Project Size: About how big is your project file? Is it in a Production? Approximately how many clips are involved in a rough estimate
Media Storage: Are your Scratch Disks set to your Documents folder or the same as project, and is this the same as the Media drive?
Also, if you could please let us know the following, this is also helpful to know:
Does it affect all projects or only some? What about new projects with a few sample clips?
Do you recall which Premiere this was last working in, when It started, and what might have changed? Any plugins, OS update, drivers, etc.
Screen Recording: If possible, include a recording of your screen showing the issue as that’s helpful.