SQL & PL/SQL :: ORA-04023 / Object (trigger Name) Could Not Be Validated Or Authorized

We are adding a column to a table using online redefintion,so its dependent triggers are getting Invalidated.

Table has 3 simple triggers on it

1)Delete trigger-AFTER EACH ROW-Its insert old deleted data in some other table

2)Insert trigger-AFTER EACH ROW-Its insert newly inserted data in some other table

3)Update trigger-AFTER EACH ROW-Its insert updated data in some other table

Modified table might be under some transcation

ISSUE: After recompiling 2 triggers(Insert and Updated) they are compiled successfully but Delete trigger is erroring out with ORA-04023:Object <trigger name > could not be validated or authorized

Q1) Why only delete trigger is errored out?

Q2) How can it be resolved?