My seller answered to me something similar the first time... But now, don't respond to me.
I know about people who had this problem, and when they changed the card, they fix the problem. So, I think there's no other way.
I put the microchip of the red card in the blue card. But that didn't work, so the problem in my case is not the placement of the card in my 3DS, the only way is to change the chip...
I know that I have a bad card, definitely. That's my problem. I know others people that changing the card solve these problems.
I think it was coincidence. But try again, you can get lucky.
Same problem with 3DSLink... I tried with several games and microSD
Have you been playing 20-30 minutes pushing the card?
Sometime takes longer to freeze.