Fatal: The remote end hung up unexpectedly error: RPC failed

Application – GITLAB

We have been facing intermittent issue with GITLAB. Users are not able to do, a) Git status, b) git clone, c) git pull Errors – fatal: The remote end hung up unexpectedly error: RPC failed; HTTP 401 curl 22 The requested URL returned error: 401 … remote: HTTP Basic: Access denied fatal: Authentication failed for

Few errors we noticed in unicorn.log

ERROR – omniauth: (ldapmain) Authentication failure! invalid_credentials encountered. I, [2018-02-12T11:08:00.926120 #2992] INFO – omniauth: (ldapmain) Callback phase initiated.

This issue is intermittent and coming once in three or four tries.

We already tried –

Restarting gitlab service,
Server reboot
Git client upgrade
Setting SSH keys in git client
Changing ldap authentication user
POST buffer size for both client and Server end
Upgrading to latest version 10.x from 8.14
New Installation with latest version

Nothing worked. Pl. help.