Zxx wet/dry macro applied to 1 VST seems to affect others randomly

[Polaris911]

I'm not sure if there's a bug with OpenMPT or I'm just using Zxx macros wrong.

I'm using Autotune VST effect in my OpenMPT song because I can't sing. I need to bypass the plugin at certain parts of the lyrics because the plugin actually makes it sound worse. Autotune does support PC (parameter control) events, but Bypass is not one that can be automated. In order to automate this, I set my SF2 Zxx macro to adjust wet/dry plugin ratio. Because Autotune is an effects VST and part of a plugin chain (along with compression, de-esser, etc), I had to create a blank MPT instrument which points to the Autotune VST. Then I use Zxx macro on this instrument in the pattern editor.

In my song, I have a dedicated channel for Vocals with a plugin chain assigned to the actual channel (not the instruments/samples). Adjusting wet/dry ratio in this channel doesn't work since it has effects applied to the channel. So I call the Zxx macro in a random other channel which has no VSTs applied to it.

This approach works great for toggling my auto-tune VST. But for some reason, the wet/dry ratio sliders on other instrument VSTs keeps changing from 100% wet, 0% dry to seemingly random values e.g. 7% wet, 93% dry. In effect, causing them to be muted. I can see this in the General tab, under Plugins > Mix Settings there's a slider. I keep having to move the slider back to 100% wet. What am I doing wrong or is this a bug?   

tl;dr Zxx macro for wet/dry ratio applied to a specific VST plugin seems to be interfering with wet/dry ratios on other VST instruments

[Saga Musix]

Are any of the plugins that are changed randomly by any chance associated to an instrument that is used on the same channel as your Dry/Wet Zxx macro at some point in time?

[Polaris911]

No, but the plugins that seem to be affected are both seperate Kontakt 5 instances if that helps?

[Saga Musix]

It's pretty much impossible that a macro would be modifying two plugins at the same time, not even if it's the same plugin type. Can you maybe try to provide a cut down version of the module you are having issues with (remove samples / plugins that don't contribute to the issue)? Can also be via private message. Without looking at the specific file, I think there is little I can do apart from the guesses made above.