I’ve had this problem with both RawTherapee 5.8 & 5.9. When I attempt to convert the Raw file the preview and converted file both look like a bunch of noise or snow. Ultimately I have to choose another file within the series to successfully convert and work with.
Hi and welcome to the forum.
You should give us some basic details, like what kind of camera is producing the file, what OS, and perhaps post a problematic raw file.
If I remember correctly I’ve had this problem with several cameras shooting Raw but currently it’s iPhone 14 plus in Raw mode and attempting to convert the .DNG files on a Windows 11 system with no Anti-Virus. I can upload a sample if possible.
If I remember correctly iPhones aren’t supported by RawTherapee, let alone Apple’s ProRAW format.
Upload a sample RAW from your current iPhone so we can have a look.
EDIT
Just looked/searched github and you might want to read this: PR#6036.
The mentioned DNG converter can be downloaded here (free, but not open source).