Stock reservations - no parameters set but AX is reserving stock

Please urgently help with this, there are no parameters set to reserve stock, and users are saying that they DO NOT tick the “reduce quantity” on picking slips, what other things could i go and look at, as to why stock is being reserved. it does not happen to all orders and all lines, it happens randomly which does not even make sense. Please point me in the right direction of where i could possibly go and check any other settings that could be causing this.