The security update for SharePoint 2016 in April 2025 will not install. This is not like the past where some processes are locking DLLs preventing them from updating.

SharePoint 2016 update: Description of the security update for SharePoint Enterprise Server 2016: April 8, 2025 (KB5002692) – Microsoft Support

This will fail to install due to a DLL that is signed incorrectly. The OPatch logs will show the DLL fail the verification. Find your Opatch logs by going to %temp% and opening sts-x-none_MSPLOG.LOG. Look for the following line:

 Assembly Error:Strong name signature verification failed for assembly '%1'.  The assembly may have been tampered with, or it was delay signed but not fully signed with the correct private key.
Microsoft.Office.Project.Server.PWA,fileVersion="16.0.5493.1000",version="16.0.0.0000000",culture="neutral",publicKeyToken="71E9BCE111E9429C",processorArchitecture="MSIL" 

Currently there is no fix for this issue. I will be updating this post as information becomes available.