This is using MS Windows 2012 R2 AD. There is only one DC with all the 5 FSMO roles, DNS, DHCP roles. Recently, found that the domain logging in were getting slow. Users have to wait some time before they were shown they are logged in. Another issue is, they seem they can't access to the file servers, look like the permissions issue.
The temporary workaround is in the morning, we have to system reboot the DC, and all these above issues are gone (for a time being). What could be the issue? How to troubleshoot?
I did checked through the DNS, sites and services, domain, and user & computers; all looks working fine.
Thanks in advance.