In MD04 STO cannot delete, GR & IV already done

Hi Experts,

Scenario is STO (Intercompany) appearing in MD04. STO created in 2010. User needs to delete it. GR & Invoice already done for this STO.

STO was created in 2010, still it appearing in MD04 after MRP run also for supplying plant.GR & Invoice already done for this STO. But delivery & PGI not done.

I have checked currently situation is.

1. Supply plant-DE59, Receiving plant- 90NL.
2. Storage location FG01 not assigned to plant 90NL.
3. Material-42767 has deletion flag at plant 90NL level.
4. Customer also not assigned in vendor master.

When trying to delete PO then below error appears.

Plant 90NL and storage location FG01 not defined (Please check your input)

Message no. ME005

Can anyone please suggest removing this STO from MD04 as it is lying from 2010 & it is 2014.