I have unallocated items to make sure all stock allocated is in stock. I did this to allow me to go into setting, parameters and tick the 'allow negitive stock' box as the is currently ticked. However when tried is says 'can't change as one or more items have negative values'. 

On the screen it shows all is correct with stock-allocated-free stock but activiaes show differences which match when run a 'respective stock valuation' report. 

Anyone have any ideas of how to resolve this.