When someone reports intermittent problems logging in remotely, my first thought is possible problems in accessing the authentication server. But the posted config shows no authentication server and that authentication uses local. So we need to look for something else.
The next thing that I thought about was the ACL used to restrict access to vty. I note that you are using an extended acl and I wonder why? I note that it restricts access to only tcp port 22. But that is not needed because the config of the vty excludes anything other than SSH. My experience is that acl used for access-class is usually not effective in filtering on destination addresses, but your acl does seem to differentiate. Is this running on real equipment or is it on some emulator. I would suggest changing to a standard acl. But I believe that the acl is not related to your experience of intermittent problems with remote access.
My best guess about the intermittent problem with remote access is based on the observation that you have only 5 functional vty ports (no exec is configured on all other vty ports). If all 5 ports report they are active/connected than attempts to access will fail. When someone logs off (or is timed out due to inactivity) then your remote access is successful.
HTH
Rick
