hmmmmm try this
step 1 take sd card out
step 2 copy all contents to a folder on your computer or pc
step 3 once all items are copied to folder delete all items from sd card
step 4 enter sd card back in this should launch a sd card removed error
step 5 once 3ds screen is like it was when you first got it take out sd card
step 6 copy all stuff from previous folder to your sd card after entering it into your computer
final step enter sd back and it should work
note make sure to delete theme that crashes