Pitch knob broken tuning when using Zynaddsubfx LMMS 1.2.1

This bug exists in LMMS 1.2.1 but NOT in LMMS 1.2 rc8 (if I remember correctly the bug existed in 1.2.0 stable as well).

How to reproduce:
-Open LMMS 1.2.1
-Choose the ZynaddsubFX preset Organ -> Organ 1 for example (the problem will be easier to hear than with the default sine wave)
-Clone your instrument and detune one of your instruments using the pitch knob to -50 cents (which is half a semitone). Now you can use quarter notes!
-Make the microtonal chord that you see in the pictures attached
-Play it, it will sound detuned
-Save the project, close LMMS 1.2.1, open LMMS 1.2.0-rc8 and play the same chord again. This time it will sound different (and it will sound how it should sound)!

The difference will become more obvious if you start making a longer microtonal melody in this way especially if it has some chords in it.

Also if the detuned note is played on it's own it will sound different in the different LMMS versions.

My OS is Linux mint


Start by reproducing the pitch-knob behavior in LMMS 1.2.1 with the ZynaddsubFX Organ - Organ 1 preset, then compare the same saved project in LMMS 1.2.0-rc8. Trace the pitch-knob and ZynaddsubFX tuning path; done means the -50-cent detuning and resulting microtonal chords sound consistently across the affected versions.

Written by the indexing model from the issue text.