What exactly is multi accounting? and is it that some gamblers do not know when they are defaulting on that?
Multi accounting is creating more than one account for abuse and cheating. Casinos prohibit this, and against it, they strongly specify this in their terms, which will result in a ban
Asides opening multiple accounts in a casino, what else can cause it because the gamblers are always claiming that they do not have another account, and the casinos are not always providing proof of the other account when they make the accusation.
It's always their words against the words of the players, and the casino will not post their evidence.
1xbit is notorious for this, it's better to play in a reputable casino and be sure to check if any member of your family is already playing in the casino you're playing.
If you think you are innocent and there's a big amount involved, then contact askgambler and file a complaint
https://www.askgamblers.com/casino-complaints, they can help you resolve your multiple accounting issues.