April 2023 CU includes the new AMSI security feature for SharePoint Server 2016 (see here for details).
This functionality caused problems on SharePoint Server 2016 machines installed on top of Windows Server 2012 R2 as AMSI relies on functionality in the Windows operating system which is only available in Windows Server 2016 and later.
With June 2023 CU for SharePoint Server 2016 we released a fix for this issue.