Getting OperatorError.OPERATOR_NOT_SUPPORTED in exception using Google Api v201603 PHP library

Hello everyone,
I am using Google Ads Api-v201603 (PHP Library) where sometimes, I am having an issue with my request which is returning me an Exception,

{"faultstring":"[OperatorError.OPERATOR_NOT_SUPPORTED @ operations[0], RequiredError.REQUIRED @ operations[0].operand, RequiredError.REQUIRED @ operations[0].operator]","faultcode":"soap:Server","detail":{"ApiExceptionFault":{"message":"[OperatorError.OPERATOR_NOT_SUPPORTED @ operations[0], RequiredError.REQUIRED @ operations[0].operand, RequiredError.REQUIRED @ operations[0].operator]","ApplicationException.Type":"ApiException","errors":[{"enc_type":0,"enc_value":{"reason":"OPERATOR_NOT_SUPPORTED","fieldPath":"operations[0]","trigger":"","type":null,"errorString":"OperatorError.OPERATOR_NOT_SUPPORTED","ApiError.Type":"OperatorError"},"enc_stype":"OperatorError","enc_ns":"https:\/\/adwords.google.com\/api\/adwords\/cm\/v201603"},{"enc_type":0,"enc_value":{"reason":"REQUIRED","fieldPath":"operations[0].operand","trigger":"","type":null,"errorString":"RequiredError.REQUIRED","ApiError.Type":"RequiredError"},"enc_stype":"RequiredError","enc_ns":"https:\/\/adwords.google.com\/api\/adwords\/cm\/v201603"},{"enc_type":0,"enc_value":{"reason":"REQUIRED","fieldPath":"operations[0].operator","trigger":"","type":null,"errorString":"RequiredError.REQUIRED","ApiError.Type":"RequiredError"},"enc_stype":"RequiredError","enc_ns":"https:\/\/adwords.google.com\/api\/adwords\/cm\/v201603"}]}}}

Same code is working for many requests but some times it returns this one.

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