Hi Cowbait,
I came across your problem as I was searching some 128gb micro SDXC Cards and sadly may be able to help you. I was caught by SD micro disks on ebay which looked ok and good value and had similar problems.
They worked well at first and then as the card began to be filled up problems accessing photos and video clips started. Reformatting cleared it but again started going wrong as card filled up.
Took me quite a time of investigating before I found the problem.
I too used h2testw and I got similar results as you did but it still read as a 128gb card.
What happens in a fake is that it is a micro SD Card but of poor quality with only say 7Gb of memory as in your case but the headers have been altered to read 128Gb. The packageing is often of a good quality and looks genuine.
Then as you load up to 7Gb all works ok but after that any further downloads rolls back to the first area of the chip and overwrites your data corrupting it.
Your problem sounds exactly like what I was caught with and from EBAY. I wouldnt buy from them at all and would us a reputable store (Like Currys PC World and have had no trouble since)
There are quite a bit of info about fake sd cards on the internet if you Google it.
Hope you get sorted out, but looks like you may have to find a good one some where else and put it to the test before useage.
Best Regards
Jim
