WiX v4 Bundle not performing Minor Upgrades when migrating from InstallShield

I'm migrating an installer from InstallShield to WiX v4 with Bundle and having issues with minor upgrades. Here's my scenario:

Current Versioning Scheme:

• Format: x.y.z.a where:

  • x = major version (static for minor upgrades)

  • y = minor version

  • z = usually 0

  • a = build version

• Minor upgrades occur when any number except the major version changes

• Major version changes result in a separate installation with different upgrade/product codes

What I've Done:

1. Decompiled InstallShield MSI to preserve GUIDs and components

2. Created WiX MSI project with proper versioning

3. Created Bundle project to package MSI with prerequisites

The Issue:

The minor upgrade functionality isn't working as expected. Here's my configuration:

Product.wxs (msi project)

<Package
Codepage="1252"
Name="$(var.ProductName)" 
Language="1033" 
Version="$(var.ProductVersion)"
Manufacturer="$(var.ProductManufacturer)" 
UpgradeCode="$(var.UpgradeCode)"
ProductCode="$(var.ProductCode)"
InstallerVersion="200">

<Upgrade Id="$(var.UpgradeCode)">
    <UpgradeVersion Minimum="$(var.InitialVersion)"
                    Maximum="$(var.ProductVersion)"
                    Property="PREVIOUSVERSIONSINSTALLED"
                    IncludeMinimum="yes"
                    IncludeMaximum="yes" />
</Upgrade>

<InstallExecuteSequence>
    <RemoveExistingProducts After="InstallInitialize"/>
</InstallExecuteSequence>
<!-- ... rest of package configuration ... -->

Bundle.wxs (bootstrapper project)

<Bundle Name="$(var.ProductName)"
    Version="$(var.ProductVersion)"
    Manufacturer="$(var.Manufacturer)"
    UpgradeCode="{01F40945-4195-4FBE-886C-2F1137F21D6B}">

<RelatedBundle Action="Upgrade"
               Id="{01F40945-4195-4FBE-886C-2F1137F21D6B}"/>
<!-- ... rest of bundle configuration ... -->

I'm testing with an initial version of x.y.0.0 trying to upgrade to a version with the same major and minor version but an incremented build version.

My Suspicion:

The issue might be related to the Bundle's UpgradeCode, which is a new addition compared to the InstallShield setup.

Has anyone successfully implemented minor upgrades with WiX v4 Bundles? What am I missing in my configuration?