VST3 and AU behave differently in Ableton 10

Hey all,

I made a simple sidechain compressor plugin.

The vst3 and AU versions work properly in Reaper: Audio comes into plugin, I send the audio from another channel to 3/4 and route that to the plugin’s sidechain, it outputs the main signal.

However, in Ableton Live 10, the AU version works properly, but the vst3 version outputs silence if the ratio is greater than 1.

Before i even ask what’s wrong, i’m more curious as to why the vst3 would behave differently in Reaper and Live? And why would a vst3 and an AU behave differently within the same DAW (Ableton)?

I wonder if it’s how I set up the input channels. But, if there was a problem with that, I would think it just wouldn’t work at all.

#ifndef JucePlugin_PreferredChannelConfigurations
         : AudioProcessor (BusesProperties()
                         #if ! JucePlugin_IsMidiEffect
                          #if ! JucePlugin_IsSynth
                           .withInput("Input",  juce::AudioChannelSet::stereo(), true)
                           .withOutput("Output", juce::AudioChannelSet::stereo(), true)
                           .withInput("Sidechain", juce::AudioChannelSet::stereo(), true)

bool CenterDuckComp2AudioProcessor::isBusesLayoutSupported (const BusesLayout& layouts) const
    // the sidechain can take any layout, the main bus needs to be the same on the input and output
    return layouts.getMainInputChannelSet() == layouts.getMainOutputChannelSet()
             && ! layouts.getMainInputChannelSet().isDisabled();

I’m on a Mac/Mojave, JUCE 6.0.4, Ableton Live 10.(most recent) , Reaper 6.12