Incorrect Pricing

We are having repeating issues with customers randomly jumping price list for no known reason.
The sales order entered (F4211) has one Price Adjustment (ASN) when the customer master (F03012) for the customer the order is for is on a different price list.
So far, no pattern has been identified and it appears to be quite random. We have different users entering the order, different customers for which the order has been entered. Also reviewed the Sales Ledger for affected orders to see if this reveals any clues as to when & how the wrong price list was applied.
Does anyone have any suggestions please?