[Q] Need Help with Write Protected External SD Card topic

Hello,

I need some help with my external SD card, please.
I've Googled this quite a bit and found many with related problems, but no solutions.

From time to time, it's hard to tell what triggers it, I notice I can't write any files to my external SD card.
My guess is the card either becomes write protected, or all apps loose permission to write to the card.

To enable writing again I can unmount and then remount the card from the system menu (don't need to physically pull card).
The last time I tried this I noticed, using ES, the external SD containing lots of files named the sign for «mu» (looks like a u), 0 bytes in size.

I've tried rebooting the phone, pulling the card, and reformatting the card.

I'm on an international, unbranded, stock, unrooted, Android 4.3 Galaxy S3.


My questions are as follows:

1) Does anyone know the cause of this problem and how to solve it?

2) Falling that, is there an app that can automatically unmount and then mount the external SD card, perhaps even as a Tasker plugin?


Thanks for your help! :)