ISDT Q6 Lipo Charger -- Self Check Failed

I really like this Lipo charger but I found a problem and don't have the answer to fix it. If you can point me in the right direction, please do. I would like to have this charger work out. It really is a nice charger.
I have had the charger for about a month and maybe charged 25 to 35 packs. RMRC said they would replace it. I would rather find out what is wrong and fix it.

When it failed it gave a code 407-3

Please comment what this code means.

Видео ISDT Q6 Lipo Charger -- Self Check Failed канала 232nate