Hi Alex,
Maintain Sloc3 in "Prod. Stor. Loc" field in MRP2 view for the material "XXXXX" and also maintain Sloc2 for the material "AAAAA". Because this field act as both production storage location as well as Issue storage location. To maintain external procurement storage location, you have to maintain Sloc1 in "Storage Loc. for EP" in MRP2 view for the material "AAAAA".
Thanks