just found where is the problem with preview image on Mighty 8K
You have swapped images, when using the SDK. First preview image must be the big preview - 400x300 size image, second image 200x125
I have opened the sliced file in UV tools, switched the preview images ( 1 to 2 and 2 to 1 ) and now the preview on printer is working.
So please fix in in next release, should be easy. Thank you.