I just recently bought a 32GB Micro SD card with USB reader.

I had a strange set of errors where I was trying to move some files on to it from my Ubuntu 16.04 system.

The first error I noticed was "Input/Output Error" then "Read-Only File System" error from mv after it copied about 4 times.

Then in dmesg I found:

Then later:

Putting a new vfat file system on didn't help.

I then ran badblocks and it after a while spit out a ton of addresses.

But then I decided to simply wipe off the contacts of the Micro SD card with a piece of soft fabric & do the same to the SD Adapter.

Strangely badblocks is claiming the card is good now. Can smudgy or otherwise dirty contacts cause all those problems?

Nevermind, guess must be bad card after all.

The system once again is randomly telling me "Read-Only File System".

The store I got it from already processed me a refund, but was hoping to maybe save the card but it looks hopeless.

nvm

Here's an old-fashioned shot to nothing to try.

Get a toothbrush with a little toothpaste, (which is abrasive) and scrub the contact area which is usually brass or copper alloy. Clean off, and try.

91% alcohol works for this as well. I remember reading about using it to clean circuit boards after a repair is made to them. Same way as the toothbrush.

Yes, that would do it. The big one to avoid is the can of switch cleaner. You get away with aerosols usually, but it's funny to see the eyes popping in guys who let that get on pcbs when the pcb starts melting The older cheap type with some cardboard(?) type stuff plastic coated were the most susceptible.