some small quantity of carts which sold few months ago may have this problem, but now it already fixed
You can save at all, or you just lost all save data at some point? You did not give any details of your problems, so i can't say anything
The last time I messed with my Super Everdrive was a couple months ago. I came home one day and turned it on and noticed my Super Metroid had no save data. So I looked in the SEVD folder and it was empty. I tried loading up other games and as I loaded them, new saves were created but all my old saves were gone. Sorry it took so.long to reply, I've been busy lately.