R12 - XLA - After running Validate AAD program, why the XLA dynamic package becomes invalid?

Subledger Accounting uses dynamic package to generate the journal entries.
Depending on the rules (AMB Setup and Event Model) the dynamic package will be created, when the Validate Application Accounting Definition program has been run.
The package will be generated with the naming convension XLA_{5DIGIT_APPL_ID}_AAD_{SEED_CUSTOM}_{6DIGIT_AAD_HASH}_PKG.
AAD_HASH value will be found in xla_product_rules_b.product_rule_hash_id.

Examples for dynamic pakcages:
XLA_00555_AAD_C_011117_PKG
XLA_00200_AAD_S_000012_PKG

Examples for errors:
PLS-00103: Encountered the symbol "THEN" when expecting one of the following:
PLS-00103: Encountered the symbol "NVL" when expecting one of the following:

This error may occur mainly due to two reasons:
a) Missing source, which is used in the setup.

   SELECT * 
   FROM xla_conditions xc
   WHERE application_id = &appl_id
   AND xc.source_code IS NOT NULL
   AND NOT EXISTS (SELECT 1 
                   FROM xla_sources_b xsb
                   WHERE xc.source_application_id = xsb.application_id
                   AND xc.source_type_code = xsb.source_type_code
                   AND xc.source_code = xsb.source_code);

b) Wrong conditions in setup.

   SELECT application_id,amb_context_code,entity_code,event_class_code
         ,accounting_line_type_code,accounting_line_code
         ,segment_rule_detail_id,description_prio_id
   FROM xla_conditions xc
   WHERE application_id = &appl_id
   GROUP BY application_id,amb_context_code,entity_code,event_class_code
           ,accounting_line_type_code,accounting_line_code
           ,segment_rule_detail_id,description_prio_id
   HAVING COUNT(*) > 1
   AND SUM(NVL2(source_code,1,0)) SUM(NVL2(logical_operator_code,1,0)) + 1;

For (a), check any patch available in MOS for the missing source. Otherwise, contact Oracle Support.
For (b), check the conditions of the JLT / JED / ADR, whether anything is wrongly entered or not.