EQs and QuickEffect disabled by inaccessible controls

[ronso0]

I experienced this once while working on https://github.com/mixxxdj/mixxx/pull/4667, and I thought it was caused by switching between main and 2.3 while testing.
Now this was also reported on the forums https://mixxx.discourse.group/t/reloop-terminal-mix-2-equalizer-knobs-not-working/24924/12 and we figured it was caused by the same controls. The forum user appearantly had this issue right from the beginning after installing Mixxx.

Interestingly we both use a Reloop TerminalMix2/4, though I'm like 80% sure I didn't use the controller while working on the EQ preferences page.
EDIT: the forum user also had a main (2.4-alpha) installed earlier.

These controls are stored with '0' in the config:
[EqualizerRack1_[ChannelN]]
group_[ChannelN]_enable 0

[QuickEffectRack1_[ChannelN]]
group_[ChannelN]_enable 0

These are not used in the TerminalMix mapping.
Removing those lines restores the EQ and QuickEffect.

[ronso0 (ronso0)]

controls are created in EffectChainSlot::registerInputChannel, but I can't trace where the crucial toggle command comes from.
I managed to reproduce the issue for [QuickEffectRack1_[ChannelN]] with 2.3 when switching between Shade and Deere and messing with Pref > EQ (clear EQ effect and tick "Bypass EQ processing")

[ronso0 (ronso0)]

Hopefully just happens when switching back to 2.3, but if it happens this is impossible to fix, except you know what you're looking for (like in the forum thread), so this report is actually just documentation of my experience so others know it, too :)

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/10737