Hello @Konnestra,
Disable polypaint, and any applied textures to rule out an issue with an applied material for those tools. Polypaint can be toggled off in the Polypaint palette, or via the paintbrush icon in the Subtool entry in the Subtool palette. Render the tools only with a default ZBrush material active.
If that produces no change,restart ZBrush and use the Tool> Load Tools From Project function to load all of your tools for the ZPR in question into a completely new session. Attempt a BPR render.
If the problem disappears, then it’s an issue with your original file, probably due to a BPR filter or render setting. Those settings are saved in project files.
If the issue persists, then there may be a problem with your installation, and you will need to contact Pixologic Support.
Thank you!