While creating a work order from an Intercompany Sales Order it is just a regular non-intercompany transaction.
There is a chance of getting error while saving that work order.
For resolving the error and to build a Work order record from the Intercompany Sales Order created from Intercompany Purchase Orders:
1. Edit Intercompany Sales Order
2. Under Items tab > unmark CREATE WO checkbox > click Save
3. On the Intercompany Sales Order, click on the item line Work Order link
4. On the Work Order, remove the Intercompany Customer which defaulted from the Intercompany Sales Order where it was created from
5. Leave Customer field = blank ( if the field is mandatory, select a another customer name)
6. Click Save