AADSTS70002: Error validating credentials. AADSTS50013: Assertion is not within its valid time range. error in memory dump using WinDbg - windbg

Question

Recently we had a production deployment of normal windows store app. It was working fine for few days and after some days performance is very very slow. Our application follows Gate keeper pattern where store app hits gate keeper and gate keeper to rest service and rest service to database (everything is hosted in cloud).
After analyzing we found that Gatekeeper web app is taking more time to respond. We have taken memory dump for the web app and analyzed using WinDbg and found an issue with AAD access token where lock count is measured as 2. And attached is the result taken from memory dump.
Here is the actual code to get access token (we are using cert based authentication)
public static void GetCert()
{
try
{
var clientAssertionCertPfx = Helper.FindCertificateByThumbprint(WebConfigurationManager.AppSettings["CertificateThumbPrint"]);
AssertionCert = new ClientAssertionCertificate(WebConfigurationManager.AppSettings["ida:ClientID"], clientAssertionCertPfx);
}
catch (Exception ex)
{
throw ex;
}
}
public static async Task<string> GetAccessToken(string authority, string resource, string scope)
{
try
{
string userName = "";
GetCert();
var context = new AuthenticationContext(authority, TokenCache.DefaultShared);
AuthenticationResult result = null;
var bootstrapContext = ClaimsPrincipal.Current.Identities.First().BootstrapContext as System.IdentityModel.Tokens.BootstrapContext;
if (bootstrapContext != null)
{
userName = ClaimsPrincipal.Current.FindFirst(ClaimTypes.Upn) != null ? ClaimsPrincipal.Current.FindFirst(ClaimTypes.Upn).Value : ClaimsPrincipal.Current.FindFirst(ClaimTypes.Email).Value;
if (!string.IsNullOrEmpty(bootstrapContext.Token))
{
UserAssertion userAssertion = new UserAssertion(bootstrapContext.Token, "urn:ietf:params:oauth:grant-type:jwt-bearer", userName);
AuthenticationContext authContext = new AuthenticationContext(authority);
result = await authContext.AcquireTokenAsync(resource, AssertionCert, userAssertion);
return result != null ? result.AccessToken : null;
}
return null;
}
else
{
return null;
}
}
catch (Exception ex)
{
LogErrorDetails objLogDetails = new LogErrorDetails();
ErrorLog objErrorLog = new ErrorLog();
objLogDetails.ErrorDescription = ex.Message;
objLogDetails.ErrorNumber = ex.HResult;
objLogDetails.strErrorContext = "Helper";
objLogDetails.strErrorContextArea = "GetAccessToken";
objLogDetails.strTrace = ex.StackTrace;
await objErrorLog.InsertErrorLog(objLogDetails);
return null;
}
}
While running this code locally we are not getting any issue with the access token and it is fast. Only in production environment performance is very slow and not sure it is with the access token or any other parameter.
Could you please help us in analyzing what went wrong with our code.