Hello  @Murmaider 

Thank you for starting a detailed post.

It's good step to verify SD Cards (to confirm the SD card itself is fine) and trying some other tips mentioned in this FAQ like unplug the SD card and plug it back in.

What should I do if the SD card doesn’t work properly on my camera?

Please also try a different SD card if you got one. 

If the problem persists despite the above troubleshooting steps, the certain camera could be defective, and it is recommended to reach the retailer or our local support to check the warranty.