At its core, KB4023814 was a aimed at addressing a growing list of performance regressions and reliability bugs that had been introduced by previous security updates.
Many enterprise environments noticed that after installing the March 2017 security updates, domain-joined computers took 10–15 minutes to log on, especially over VPN. KB4023814 fixed a race condition in the Group Policy client (GPSVC) that caused timeouts when processing large GPOs. kb4023814