I have used the Mixer service several times but never sent it directly to a centralized exchange because I knew it would be dangerous if it was detected and the balance would be held, use another wallet to be safer, but this is not entirely YoMix's fault because the Uphold exchange itself has strict regulations.
There's no different for using another wallet, it's a concealing and they can easily recognize if the funds was come from mixing service.
I know mixing is not money laundering but look at this:
1. Mixer receives money from someone who has done illegal activity.
2. Mixer stores that money on address A
3. I create a mixing order, deposit money to mixer and hours later I declare address B where I want to receive money.
4. Mixer sends me money from address A to address B. Address A has received money from someone who has done illegal activity, so there is a chain: Laundered money -> Address A -> Address B that belongs to me. This is probably what exchanges see and it's very hard to convince them that you are not associated with illegal activities.