Sometimes .. happens to Jodie a lot.. you'll be adding multiple scope lines to a WO and suddenly it wont let you add more..
The fix is in sql..
go into tab-scope_web
search the offending WO number.. find the ID of the "blank" scope line and delete..
example:
Table: [tab-scope_web]
where [wo_number] = '55265603'
DELETE FROM table_name WHERE condition;
example
delete from [tab-scope_web] where [id] = '894261'