"Cannot raster a malformed PDF file"

When creating a quote I can see a PDF representation of the quote at the bottom of the screen. However, when I click on the View PDF or Email Quote buttons it just shows a grey background instead of the quote with the error message “Cannot raster a malformed PDF file”.

I am running the latest version (v5.4.9-M85) in a Docker container on a Synology NAS.

Solved by changing the app url in the env file.