That warning has been explained a hundred times. It is just a notification that your wallet registered a different kind of block. That is because of segwit and no problem at all. It's just a notification you can ignore.
Your balance being incorrect seems unlikely. The balance you see on the block explorer is the correct balance. You should try to run a repairwallet command. Make sure to always have a backup of your wallet.dat. Repair wallet will reread the blockchain and should come up with correct balance.
Repair and rescan already done and my coins are still missing...
Basically, all the staked coins are gone!
You can't deny there still an issue from the start with staking with this coin...