So after 5 days here is my response from C-Cex.
Hello! Wallet responded with error message on attempt to create transaction. Usually this happening when there is an issue with blockchain, wallet has limitation on transaction size or amount of coins in one transaction. Your funds are back to Your balance. Let us know if there is anything else we can help you with. Thanks!
This begs the question, what is the absolute maximum size and/or coin amount in a single transaction?
Size in bytes is probably the problem here. Ive had trouble sending transactions for this reason.