Project fails to load after VB6 upgrade wizard: re-run conversion or restore the pre-upgrade baseline?

Failed upgrade leaves a partially converted project

A VB6 project processed by the Visual Studio Upgrade Wizard can end up in a mixed state: a new .vbproj exists, but it fails to load or build in the target IDE, while some source files were converted and others were not. The documented failure condition here is the project file being reported as incompatible or corrupted at load time, though the exact error text varies by Visual Studio version and should be recorded from the Output or Error List window in the failing environment rather than assumed.

Constraints

A pre-upgrade snapshot exists (source control commit plus a full directory copy), and the original VB6 environment can still rebuild the baseline. The concern is that continuing development on the partially upgraded output risks hidden inconsistencies, since it is not always clear which files the wizard modified. Third-party COM references may also fail independently of the code conversion, complicating diagnosis.

Open questions

• After a partial conversion, should recovery always restore the pre-upgrade baseline and re-run the wizard, or is manual repair of the partial output ever the safer option?
• What verification (clean rebuild after deleting bin/obj, comparison against baseline behavior) is sufficient to confirm the recovered project is trustworthy?
• Does the IDE version used for the re-run change the outcome, given that project schemas and default target frameworks differ across Visual Studio versions?