Volume changes when I hide Halion VSTi

Hi there

I’m having a strange problem using Halion 6 VSTi in Ableton Live 9.

Whenever I hide the plugin, it’s still very much playable via midi, but the volume goes down, noticeably (about 5-8dB).

I can A/B the problem by holding midi notes on my keyboard and constantly opening and closing Halion with my mouse. Every time I close the plugin there is a volume drop.

It must be some kind of internal setting in Halion, but I don’t see why the volume would be boosted when the plugin is visible.

Any ideas?