These should be exactly what the SENSOR is in dimension and you need to post process or use a viewer that corrects for sensor dimensions. Nothing is broken here. Just your RAW viewer isn't dealing with the RAW image correctly.
https://www.google.com/search?q=Lumix+GX8+RAW+VIEWER finds viewers and a CODEC from the maker.
When shooting on my Lumix GX8 camera saving in JPEG & RAW, the RAW files are horizonally compressed compared to my JPEG's and look squashed.
There's also more in the frame horizontally than the JPEG versions but not vertically.
How do I fix this?