I am just integrating the QHY 268M into my setup - too many clouds to try it outside so far.
I notice that when I use 3x3 binning on the image capture, the fits viewer still indicates that it is a 16-bit image.
I know that the plate-solver likes to use binning to simplify the problem, but binning (at 16 bits) might lead to problems.
Is your 268C image showing up in the FITS viewer 16 bits?