Could you please uncheck the use of Graphic Processor under Lightroom's preferences and check if it helps.
Unchecking the graphics processor doesn't help.
I would also light to add that I went to check the actual source file of the image (raw + jpeg) and it was ok.
It will not change the already affected files.
Try to import new images and check if they become corrupted while working or not.
Can you help me understand this.
I have checked that the actual image files are ok so I may attempt to reimport the images again as a "workaround" but this means something else is corrupted. What could it be here ? Is it the light room catalog or preview files ?