You may need a custom build of D9 to dump some flashcarts as their secure value will report as invalid.
You can also use this:
https://filetrip.net/nds-downloads/applications/download-nds-backup-tool-3in1-0-31a-f9407.html
However that one is tricky to use because unlike WoodDumper (the wifi version of wooddumper), you have to host a FTP server for it to connect to. (on your PC. Not on the internet. It won't connect to internet FTP servers).
This works best on DS Lite. however it's feasible to use it on 3DS now. But you'll need to modify my Action Replay Stage3 bootstrap to boot it. (rename it to ActionReplay.nds and replace the one my stage3 bootstrap uses).
That way it does a card reset before booting this tool. Note however because DLDI support for 3DS SD isn't yet available, it will always use default IP and login info. It will be displayed on screen when it boots. You may have to reconfigure your router and make sure your PC is using that IP it expects. No way around that for now.
This tool was the only one that dumped my DS-Xtreme correctly so it can be useful for dumping some carts that cause issues.