Trying to add an invalid DLL (e.g. a VST3 DLL) as a plugin results in a series of three message boxes in the scanning process:

• First the plugin is tried to be loaded using the regular bridge. This fails, so OpenMPT offers to load the plugin natively without the bridge.
• Confirming that makes the plugin fail to load natively because it's still not a a VST plugin. This will of course also fail
• Now OpenMPT tries another time to load the plugin through the legacy plugin bridge. Again it will offer to load the plugin natively instead.

The correct flow here would be:

• Try to scan plugin using the normal bridge.
• If that fails, silently fall back to the legacy bridge. If that works, the legacy bridge should be force-enabled for that plugin.
• If that also fails, only then ask the user if they want to try scanning the plugin without the bridge instead.