OneOf property is failing during OAS Schema Validation

Hello Team,

Requesting you to please check this issue and help. Performing schema validation with oneOf, discriminator and mapping property in oas3.0.

Error:

{
"fault": {
"faultstring": "OASValidation MAM-EXT-SpecValidation with resource "oas://openapi.yaml": failed with reason: "[ERROR - An error occurred during schema validation - com.google.common.util.concurrent.UncheckedExecutionException: java.lang.NullPointerException.: []]"",
"detail": {
"errorcode": "steps.oasvalidation.Failed"
}
}
}

yaml file looks like:

Json payload looks like:

--data '{ "billableHeader": { "sourceSystem": "UPSTREAM_APP", "sourceTransactionType": "INVOICE", "eventType": "BATCH", "messageCreationDatetime": "20220811140203", "timeZoneCode": "GMT", "isBulkProcessing": true, "**product": "Airlcl"** },

Start by reconstructing the OpenAPI 3.0 schema from the attached YAML images, focusing on the oneOf, discriminator, and mapping configuration, then run validation with the shown JSON payload. No source file or test is named; trace the resulting NullPointerException and add a regression test once the failing validation path is identified. Done means the schema validates correctly or returns a clear, actionable validation error.