I'm using Mac OS 10.12.6 Sierra. Recently I've found that whenever I (rarely) reach for a usb stick to transfer images or files, they mount readonly for me. I can't seem to figure out how to mount them read-write, or what causes this.
Also the main solution I found has been to reboot the macbook pro 15 and then it'll use usb sticks normally as read-write.
It seems something to do with waking from deep sleep… but I'd like to find a way to kick it into "normal operation" without rebooting. OR to prevent it from abnormal behavior to begin with.