I format SD cards with the PC and delete files from them with the PC. Never had a single problem. Ever.
This is not surprising, as we are talking about a standardised file system.
I've heard the K-1's earlier firmware versions had issues with some SD cards. It may be worth updating to the latest K-1 firmware version to see if that changes anything.
P.S.: I wouldn't recommend attempts at fully formatting a card (as in covering every bit). This should not be necessary at all and the type of memory used for SD cards wears out over time. Life expectancy could still be more than enough even when torturing a card with deep formats, but there shouldn't be a reason for them in the first place.
Last edited by Class A; 06-23-2017 at 06:10 PM.