Spark clients not always logging into opefire

Using win server 2008r2 x64 SP1, openfire 3.7.1, spark 2.6.3.

Server is member of AD 2003r2 functional level, connecting to a 2008 domain controller.

Spark clients try and connect, go to authenticating, then come back inmvalid username/passord. If you try enough times it goes through. Aslo, spark admin console is extremely slow to respond.

Server is a fresh install with nothing else running. It’s a VM with 2 processors and 8 GB ram.