This is from a bad batch. I bought my F8 in 2016 as well from B&H in NYC. It worked well until January 2020. I've had the same card writing noise at all sample rates in SD slot 1. It's poor design from Zoom where the shielding on the SD Slot 1 goes bad or is non-existent. Zoom has not addressed this issue with all of us who have had problems. They will just tell you to take it to their service center. And in a country like India, it's just how service centres will extort money from you. It's unfortunate but this is our situation. Hope you've had some luck.
