How to downgrade in WiX v5

[stvoorhees]

I have a custom bootstrapper application that supports downgrades. I am encountering an issue similar to this. The answer to the linked question states the bootstrapper should uninstall the higher-versioned bundle.

I capture the BundleId when PlanRelatedBundleType is raised.
I uninstall the bundle manually when ApplyDowngrade is raised.

The uninstallation is successful. But I still get 0x80070666 during the Apply phase.

If I re-run the same installer (now that the higher-versioned bundle has been uninstalled), I get a successful installation.

What am I doing wrong?

Relevant log:

[2024-06-05T17:31:45]i000: Downgrade bundle: {DEV-GUID}
[2024-06-05T17:31:45]w224: Plan skipped due to related bundle of plan type Downgrade:
[2024-06-05T17:31:45]w225:     id: {DEV-GUID}, version: 1.0.0.2
[2024-06-05T17:31:45]i299: Plan complete, result: 0x0
[2024-06-05T17:31:45]i300: Apply begin
[2024-06-05T17:31:45]i000: Uninstalling related bundle: C:\ProgramData\Package Cache\{DEV-GUID}\test.exe -uninstall -quiet
[2024-06-05T17:32:10]i000: Uninstallation exit: 0
[2024-06-05T17:32:10]i399: Apply complete, result: 0x80070666, restart: None, ba requested restart:  No
[2024-06-05T17:32:10]i500: Shutting down, exit code: 0x80070666

Yes, "DEV-GUID" is placeholder.