Is this using the pattern sequencer?

Sorry you are still having trouble with this. But you didn't provide us with ANY details about what you actually did. Until you do we can't try to reproduce what you report.

I invested hours/days/weeks in an exctensive performance. Especially in the downmixing (onboard). 8 scenes ... played one by one!!!

Then I created a very clever way to decrease the volume of one sound and increase the volume of another (piano) in scene 3. This by triggering according MS Lanes.

Not sure I understand that part about 'I created a very clever way'. Why didn't you just follow the advice Bad Mister, Jason and myself gave you two months ago when you first posted this issue?

You posted this 'Automated Fade Out via MS Questions thread on 04 August 2023, a couple of months ago.
https://www.yamahasynth.com/forum/automated-fade-out-via-ms-questions#reply-122768

In that thread Jason, myself and Bad Mister provided detaile info about how to do this and also provided links to articles that would show you how to do it. This is EXACTLY what Bad Mister said there

Is there a possibility to do that for the whole performance? "Common"?

Yes. Super Knob controls Master Effect.

Is there a one-click trick to get the volume back?

Yes. Super Knob position is instantly recallable and can have a button for any two values. Example: [Knob Position 1] = 0, [Knob Position 2] = 127

For a step-by-step explanation please see this post on two different methods to control overall Volume:
https://yamahasynth.com/forum/is-there-any-way-i-can-completely-turn-down-the-volume-on-all-16-tracks-or-on-a-designated-track-at-a-designated-point-within-the-sequencer#reply-103849

Did you follow that advice you were given?
Did you use those links to the two different methods Bad Mister suggested you try?

I suggest you follow that advice or this advice that Jason gave you in that other thread

Upload your broken Performance to Soundmondo and someone will fix it and let you know what changed.

I'm guessing after the MS. completes the MS is left still offsetting volume and is not being compensated for.

We can only provide advice - it is your choice whether to follow it or not.

I suggest you reread your own thread posted two months ago and follow the advice you were given there.

Further I suggest you should ALWAYS test your setup to make sure it works properly before you use it in a gig.

Posting your perf to Soundmondo will provide the DETAILED info needed about what you did so we can see where you went wrong following the advice Bad Mister first gave you.

and begin editing the Motion Sequences in that copy, so that you don't mess up what you've made already.

I think you will find that you are alone in your advice to continue trying to use motion sequences to do this.

As Bad Mister explains in the link I provided the shortest, simplest and cleanest way is to use the Isolator Master Effect and route control of the 3 bands to the super knob.

OP is running into the reality that Jason told them about 2 months ago when they first ask this question:

I'm guessing after the MS. completes the MS is left still offsetting volume and is not being compensated for.

The clue is what OP first said in this thread:

I noticed this sh.. , that the volume can only be restored, when pressing the performance anew (live set).

Although you can also turn the MS master switch OFF and back ON to terminate the sequences.

One a control assignment uses an MS Lane as the source that MS Lane will ALWAYS provide an offset value for the parameter being controlled.

That MS offset is applied to the beginning value of the motion control curve being used. If that curve is BI then depending on the curve type and the ratio setting the curve's initial value may be well below 0 causing the actual parameter (e.g. volume) to essentially be at 0.

Before the MS is actually triggered the MS offset value will be the leftmost value in the defined curve (step 1) of the sequence. If the MS is not set to LOOP then the rightmost value of the rightmost step will become the 'forever' offset.

In either case that 'forever' offset will continue to be applied until the sequence is terminated by setting either the part or master MS switch to OFF.

Motion sequences are, as their name suggests, designed for 'motion' - thay are ill-suited for use in one-time events.

Although one can certainly use a hammer to remove a lug nut the results you get will be less than satisfactory.

OP needs to use the right tool for the job and follow the advice Bad Mister, et al, gave him two months ago for this very issue.

Montage classic discussion follows ...

I'm not at my keyboard at the moment but I have used Motion Sequence for a similar situation.

My volume "fade" is so fast in the motion sequence that it acts more like a switch. There's a synth line with parallel 4ths. The line is up tempo and compromised of 16th notes.

At the top of the run, the 4ths go away and I have notes using the same sound (without the added 4th) in the next 16th note. I couldn't press a scene button reliably to keyboard select or mute out the added 4th so what I did was generate a MS that silenced that added 4th when I reach the top note.

The motion sequence "fades" (albeit instantaneously) that Part with the added 4th and the motion sequence keeps the "fade" stuck there "forever". Or, rather, until I do something to reset that Part.

To setup adding the 4th, I have a scene button that unmutes the Part that adds the 4th transposed synth layer. This scene button also resets my motion sequence so I rearm the "fade" again which occurs when I hit the same high note in the run.

I elected to do things this way since the same fast run with the added 4th happens twice in the tune and this allows for a natural way to get that sound using a scene and then automatically cancel it at the end of the run when I strike a certain key.

As always, "striking a certain key" when using motion sequence requires using arpeggio based MS timing. MS (unfortunately) doesn't allow for restricting note ranges but indirectly this can be done by using an arpeggio since arps can be note limited. Your fade may not require note limits.

There are certainly challenges in mastering motion sequences. That said, there's no randomness unless of course you use the randomization parameter (now a available in the new Montage M). I found reset values, MS termination, and note limits (as detailed here) to be particularly nonintuitive. Persistence and experimentation pay off.