Payday Diamond Heist Accidental Quick Clear

Decided to try Diamond Heist on overkill (crazy for us because we suck) and cleared it rather flawlessly and quite fast. This probably is nothing impressive but it blew our minds since we went into this as a joke and expected to get destroyed :)

[@Tetraces]

Yep you have to get all the boxes at the same time. Also when you put the codes in, there is a VERY small chance the vault will open and you can move on, otherwise there are other things you have to do. This method is mostly luck based I believe.

[@Bailey54321100]

So basically, to do this the fast way, you all have to put the thingy on the alarm boxes together at the same time? Or doesn't have to be at the same time? Can you tell me how to do it the fast way like you did? I don't understand. Please reply.