We have a client reporting intermittent issues when logging into Umbraco CMS, when logging in using the correct credentials. It provides an Umbraco error, "oops! we couldn't log you in. Please check your credentials and try again". Just wondering if anyone has had any similar issues before or could offer any advise on how to fix the issue?

Does the issue fix itself?

It does seem to - the users are usually able to login after a few attempts