为什么我只有5%的时间出现坏数据异常

我有以下代码，大约5%的时间都在抛出CryptographicException，我不明白为什么a）它没有持续失败，b）为什么它根本失败：

// Initialize the new secure keys
var keyGenerator = KeyGenerator.Create();
var keyPair = keyGenerator.GenerateKeyPair();
this._privateKey = keyPair.ToEncryptedPrivateKeyString(privateKeySecret);
this._publicKey = keyPair.ToPublicKeyString();
// Initialize the certificate generation
var certificateGenerator = new X509V3CertificateGenerator();
var serialNo = BigInteger.ProbablePrime(128, new Random());
certificateGenerator.SetSerialNumber(serialNo);
certificateGenerator.SetSubjectDN(GetLicenseeDN());
certificateGenerator.SetIssuerDN(GetLicencerDN());
certificateGenerator.SetNotAfter(DateTime.Now.AddYears(100));
certificateGenerator.SetNotBefore(DateTime.Now.Subtract(new TimeSpan(7, 0, 0, 0)));
certificateGenerator.SetSignatureAlgorithm("SHA512withRSA");
certificateGenerator.SetPublicKey(keyPair.PublicKey);
var result = certificateGenerator.Generate(keyPair.PrivateKey);
this._clientCertificate = new X509Certificate2(DotNetUtilities.ToX509Certificate(result));
this._clientCertificate.PrivateKey = DotNetUtilities.ToRSA((RsaPrivateCrtKeyParameters)keyPair.PrivateKey);

堆栈看起来像：

System.Security.Cryptography.CryptographicException: Bad Data.
Result StackTrace:  
at System.Security.Cryptography.CryptographicException.ThrowCryptographicException(Int32 hr)
   at System.Security.Cryptography.Utils._ImportKey(SafeProvHandle hCSP, Int32 keyNumber, CspProviderFlags flags, Object cspObject, SafeKeyHandle& hKey)
   at System.Security.Cryptography.RSACryptoServiceProvider.ImportParameters(RSAParameters parameters)
   at Org.BouncyCastle.Security.DotNetUtilities.ToRSA(RsaPrivateCrtKeyParameters privKey) in C:'BouncyCastle'crypto'src'security'DotNetUtilities.cs:line 173
   at EBSConnect.EBSClientBase.InitializeSecurity(String privateKeySecret) in c:'Projects'EBSConnect'Source'EBSConnect'EBSClientBase.cs:line 78

在剩下的时间里（95%），此代码按预期工作，并且我能够使用此动态生成的证书与联邦服务进行通信。有什么想法吗？