Mono VST plugins output only to the left channel

[bladeSk]

Bug Summary

When using a mono VST plugin via VeSTige, sound is produced only in the left channel instead of both channels.

Steps to reproduce

Load this Windows VST in VeSTige https://github.com/bsutherland/JuceOPLVSTi/releases/download/1.0.1/JuceOPLVSTi.x64.dll and play any note.

Expected behavior

Same audio should play in both channels.

Actual behavior

Audio is hard-panned to the left.

Affected LMMS versions

Version 1.3.0-alpha.1.102+g89fc6c9 (Linux/x86_64, Qt 5.6.3, GCC 5.4.0 20160609).
AppImage downloaded from here https://github.com/LMMS/lmms/releases/download/v1.3.0-alpha.1/lmms-1.3.0-alpha.1.102%2Bg89fc6c9-linux-x86_64.AppImage

[Monospace-V]

For some reason, I cannot seem to use the VSTi you have linked, even in VSTHost. However, I checked the releases page and downloaded an older version of the VSTi. I can reproduce this issue on LMMS 1.2 for Windows too. It can be downloaded through the zip link on this page.

[musikBear]

solution is to inset a Stereophonic Matrix plugin, and turn all the knobs to 0.5
afair...

[bladeSk]

While using Stereo Matrix is a good workaround, it's still a VeSTige bug.

[QuixoticJk]

Id like to try to solve this as a first issue