Late supply pegged to sales order exception :planned order created fter demand due date

We are on 12.1.3 and use unconstrained planning.Items have no demand or planning time fences yet in some case we are noticing that as an example if item A has say a work order demand for 9-jan-2014 , it is creating a planned order for 15-mar-2014 for item A  and issuing a Late supply pegged to sales order exception .The work order demand is qty 1 and the planned order is also qty 1 and is pegged to only this work order demand and no other demand.since we have no time fences at all and the planned order is pegged