Duelbits will also ask for your KYC in the withdrawal process. especially for those who make withdrawals in large enough amounts. many users will probably refuse KYC, and more often than not interrupt the withdrawal process. because the KYC verification process also takes time. and until that is done, most casinos will not process any withdrawals made.
but as long as we have proper documents, and are by the procedure, the process won't take too long either.
Not only when you withdraw large amount but also if you display any irregularities on your gambling activities like to often withdraw and deposit, abuse in bonus and other things that normal players wont do frequently. The terms and conditions stated that they are allowed to ask KYC anytime without further explanation for the reason and this stated on the majority of the casino with license.
Im a small gambler in Duelbits but still I undergo a KYC before since I participate on the promotion too much which result me to be excluded on joining it because I win too often.
I had the same issue as you, got excluded from the promotions even though before that I could always participate in it. Also did full KYC in order to get my withdrawal (around 50$) but still excluded for the promotions. Could be related to the fact that I used to use a free vpn to access some sites (not for Duelbits) and probably made a slip there. Too bad as the promotions they offer are pretty interesting.