I purchased my Retra LSD last year and I only used it once, I carried it with protection bag, rinse it with clean water and stored in electronic dry box after use. But recently I found out there are many scratches/marks with regular pattern on the LSD top glass (please see attached photos).
At first I thought it was fungus/mildew growth inside the top glass, I contacted Retra and they ask me to send the LSD back for inspection. But after their inspection, they found out the scratches are on the glass surface and there's no mildew inside, they suggest that the scratches are formed probably by exposure to chemical substance and high heat, and charged me for the repairing and shipping fee which I think is reasonable if it's not manufacture or material problem.
But I doubt that the scratched/marks are formed by chemicals and heat, as I only used it for one time, I rinsed with clean water only afterwards and never expose it under sunlight for long time. And the marks pattern are so regular that I don't think it is formed by bumping with hard object.
Anyone have ideas on what's causing these marks or have similar experience? Please share your thoughts, sorry for the long essay and thanks a lot!