Update: 5th April 2018:
It has been documented that this update is failing to install on a large number of Windows 7 64 bit SP1 and Windows Server 2008 R2 systems. No known issues are listed within Microsoft’s knowledge base article.
At this time; we can only wait for further updates or information to become available. At the time of writing; it is unclear if this update will be combined into next week’s cumulative update.
Earlier this week Microsoft issued an out of band (an update outside of the established second Tuesday of each month) security update to resolve a regression (an un-intentional coding error resulting in a previously working software feature no longer working, alternative definition here) which introduced an additional elevation of privilege (defined) security vulnerability in the kernel (defined) of Windows 7 SP1 64 bit and Windows Server 2008 R2 SP1 64 bit.
While this was thought to have been resolved in March’s Microsoft Update Tuesday; the security researcher, Ulf Frisk who disclosed the issue to Microsoft stated the March updates did not resolve it.
If you maintain any of the above Windows versions in your organisation or at home, please ensure to run Windows Update to install the appropriate update.