If you solved the problem could you try to explain quickly what you did to fix it? Other users with the same issue who stumble upon this would find it useful.
Also there’s a few things in the code examples you gave I would change as such:
Firstly, ScopedPointers are depreciated so you want to replace them with std::unique_ptrs:
Second, from the code you’ve given there’s no reason to have your Slider as a pointer. You can just make it a normal object (unless you need it to be a pointer elsewhere in which case make it a unique_ptr also).
processor declared twice… Maybe this was just a typo but make sure you only have one.
Now with these changes, in Plugineditor.cpp:
PluginEditor(...) : driveKnob("Drive")
driveKnob.setTextBoxStyle(Slider::NoTextBox, false, 100, 100);
driveAttachment.reset(new AudioProcessorValueTreeState::SliderAttachment(p.getState(), "drive", *driveKnob));