Installshield 2015 : minor upgrade (Update.exe) not replacing files for one feature - .net-assembly

Question

In Installshield 2015 Premier Edition, I've created a patch definition which upgrades my application product from version 1.9.7 to 1.9.7.5
In the Installscript MSI project, I've only changed package code, product version and built the patch (Latest 1.9.7.5 release - Previous 1.9.7 release).
Patch (Update.exe) is executed under Admin priviliges (a 1.9.7 release in installed priorly)
The patch 1.9.7.5 will omit to update .exe and .dll component files of a feature application directly install in [INSTALLDIR] (root : C:\ProgramFiles\MYCOMPANY\MYAPP\confapp.exe)
All other component files are updated respectfully ; they're located in their own sub-directories of [INSTALLDIR] as designed in Installation Architecture in IS2015.
C:\ProgramFiles\MYCOMPANY\MYAPP\Feature1DIR\app1.exe
C:\ProgramFiles\MYCOMPANY\MYAPP\Feature2DIR\app2.exe
C:\ProgramFiles\MYCOMPANY\MYAPP\Feature3DIR\app3.exe
C:\ProgramFiles\MYCOMPANY\MYAPP\Feature4DIR\app4.exe
C:\ProgramFiles\MYCOMPANY\MYAPP\Feature5DIR\app5.exe
I'm shipping the newly built applications and have upgraded my .dll files with AssemblyInfo.cs.
Long story short, my Update.exe is only updating 5 out of 6 applications installed.
Any help appreciated if you've already encountered the issue,
Regards,

Answer 1

Can you please add your feature/component/file structure and log file entries that relate to those files in particular? It should look something like:
MSI (s) (B4:4C) [11:30:07:906]: Executing op: FileCopy(SourceName=eulatxt|eula.txt,SourceCabKey=FILE1,DestName=eula.txt,Attributes=512, FileSize=29239,PerTick=32768,,VerifyMedia=1,,,,, CheckCRC=0,,,InstallMode=58982400,HashOptions=0, HashPart1=-1713153497,HashPart2=58557210, HashPart3=1046945815,HashPart4=871163290,,)
MSI (s) (B4:4C) [11:30:07:906]: File: C:\WINDOWS\system32\eula.txt; Won’t Overwrite; Won’t patch; Existing file is unversioned but modified
You also need to check your components and key files. If the key file for a component is not changing in your patch (this is a "small update" or "patch" BTW, not minor upgrade), none of the other files in the component get upgraded regardless of the version changes associated. Remember that component best practices state one binary (versioned) file per component.
From this MSDN article:
Be aware how the Windows Installer applies the File Versioning Rules
when Replacing Existing Files. The Windows Installer first determines
whether the component's key file is already installed before
attempting to install any of the files of the component. If the
installer finds a file with the same name as the component's key file
installed in the target location, it compares the version, date, and
language of the two key files and uses file versioning rules to
determine whether to install the component provided by the package. If
the installer determines it needs to replace the component base upon
the key file, then it uses the file versioning rules on each installed
file to determine whether to replace the file.

Answer 2

If this is an InstallScript project, open Components view and make sure OverWrite setting is set to Always. By default, it is set to Overwrite files by version, then Date, I think. However, I have seen cases when this algorithm did not work for some reason, and some files were not updated.