Don´t use nld to downgrade. Use original DJI APP. You can find on google enough information how to do...
@Robert: No, i stay on 400. NFZ is not an option for me. Due to very hilly landscape i was very restricted in range. NLD boost improved it markable.
@nld: Still confused about your advertisement in bird map. 510 is downgradeble to 300 on mv2...
I can confirm that i was able to downgrade using IOS DJI stock app, V510-V300. After i was not able to downgrade further using NDL, tray sometimes to downgrade to V200 with goal V100 but both stop at 15% in the operation "flashing firmware to modules".
As notice, after buying MV2 i firmware version V300 was on it, i use NDL to active FCC (i buy a EU version ) and FCC was activated also after update to V510 using DJI update (by my mistake). So my reason to downgrade was to have NFZ and also to stay on a lower firmware hoping that the altitude limit would be past at last over at 1km, the full potential i don't even would use, but up to 1km i would for full panorama pictures.