They also explained the closing of deposits. Their network is not yet stable enough and there are breaks in the chain. But they are working hard on it.

Regarding deposits, here is one potential issue that could occur due to a chain split. Say you sent some NRG to the exchange and you were both off chain. The exchange accepts the deposit and you trade for a different coin/token then withdraw. After that, you both realize that your transaction wasn’t valid. Since you have already withdrawn the new coin/token, the exchange cannot undo this and because the original transaction was off chain, they don’t get the NRG you sent (you may be good about it and resend but not everyone would). Now the exchange is out those funds with no way to recover them. Multiply this by however many people do their deposits at this time and it could be a massive problem. Setting an arbitrary time for confirmations is not really a solution to this because how do you determine how long it will take for the exchange to realize they are off chain?
With withdrawing, everything is in the exchanges system so if you are both off chain, the exchange still has this information saved and can process the transaction again once they are back on chain.