Hitting JUCE_ASSERT_MESSAGE_THREAD in VST3HostContext::restartComponent

… when loading my VST3 plugin from the AudioPluginHost.

Running Juce v6.1.2 under Linux.

Comment for this assert says:
// If you hit this, the plugin has requested a restart from a thread other than
// the UI thread. JUCE should be able to cope, but you should consider filing a bug
// report against the plugin.

I’m not deliberately requesting a restart of any kind. Any clues as to the cause gratefully received.