All USB sticks mount as readonly, FAT32 or VFAT. Rebooting mounts them read-write 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.
I read an apple forum about this, A user in the forum said that if you format the pen drive to FAT32 in Disk utility you might solve your problem. Make sure you have a backup of all the contents in the pendrive because erasing it will remove all files.