Please attach the WIC diagnosis log file.
You did not mention the most important info, e.g. if the installed WIC codec can actually handle your files...
Your problem sounds to me as no WIC codec installed on your system can handle the RAW portion of your proprietary Panasonic RAW file.
But can extract at least the small embedded preview. So IMatch is will to use that.
IMatch only falls back to internal RAW processing when no WIC codec returns anything useful.
Did you ask Panasonic for an up-to-date WIC codec? They are supposed to provide one for their proprietary RAW formats.
They know their RAW formats best, after all, and can surely provide a superior WIC codec which allows all WIC-compliant Windows applications to process your files.
If Panasonic does not support the WIC standard for RAW processing, well...bust.
I suggest you switch to IMatch's internal RAW processing instead. That is a global option, switching WIC usage off in favor of using LibRAW routines.
See
photools.com RAW Processing You need to force a re-creation of cache files afterwards.
Other programs I use will display the RAW and JPG as one file but iMatch displays them separately.
Why should IMatch display separate files combined? The JPEG may look totally different than the RAW (and usually does!).
If you want this, I recommend you setup file versioning (
File Relations: Versioning) and to make the JPEG a visual proxy version for your RAW.
This way you can make your RAW look like the JPEG, stack the files neatly into one file etc. propagate metadata from the RAW to the JPEG and much more.
Or keep the RAW on the top and just tuck away the JPEG.
This works in IMatch usually much better than in "other" applications you might use. Please always be precise, because then we can help you better. "Other" applications is not helpful.
And, IMatch can do this trick even when your JPEG is named differently than the RAW, if it is in a different folder, if you have multiple versions to choose from etc.