I just tried exporting the same image from darktable using the sidecar file on a different machine to check whether it was an issue with darktable or my hardware, and I noticed none of the same issues.
Therefore, I tried a full reinstall, including wiping the database and library files in AppData. To be honest, I’m not really sure why I didn’t try that first.
Not sure what the issue was in the first place, but the reinstall seems to have fixed everything. I really appreciate the help anyway, though!