Error with request to the server: Access denied. You do not have permission to perform this action or access this resource., StackTrace

Hello,

I am a site collection administrator, and I got the above error message when I try to upload or drag and drop file to Sharepoint library.  I was able to do it on the second try.

Other users with Contribute permission also experience the same issue.  They were able to upload/drag n' drop file to Sharepoint Document Library and List before, and now users randomly seeing this error.

Network environment:

Windows 2012 R2 AD.

SP 2013 on Windows 2012 R2 with up to date with windows and sharepoint patches.

Thanks for your help.