Rendering Error in layout Message/Item: array_keys(): Argument #1 ($array) must be of type array, null given. Please enable debug mode for more information.
You could try reducing the pixel distance of the dither. Between 2 and 4 should be sufficient. You could also increase the size of the box containing the guide star to be twice the diameter of the dithered pixel distance.
Skywatcher 190MN - EQ6 Pro (with Belt Mod) - ASI1600MM-Cooled - ASI EFW7 - ASI120MM - WO f4 Guide Scope - Rigel nStep - KStars/Ekos - KDE - PixInsight
As a comparison, can you guider using the internal guider? (It's very good by the way). I've never used lin_guider so may be coming to the end of my input.
I would suggest turning OFF the dithering to measure the capture peculiarity.
The only 128 pixel reference I've seen is the option to select the 'Use Image Guiding" feature in the Guide Settings section of the Options.
Skywatcher 190MN - EQ6 Pro (with Belt Mod) - ASI1600MM-Cooled - ASI EFW7 - ASI120MM - WO f4 Guide Scope - Rigel nStep - KStars/Ekos - KDE - PixInsight