I don't think this is about presets.
I think perhaps there is something odd random behavior going on with the assign modes, the voice stealing and also when using pedal hold while some notes are held down.
I think it would be good, if Arturia had a look at it.
In Poly mode 1, then if you in example hold down some notes, then activate the hold pedal and play other notes, then the hold notes are being stolen, at some voice count.
In Poly mode 2 this work better, but normal voice stealing and retrigger function for the mode is not consistent, and using the hold pedal also introduce unexspected behavior.
And if you in Poly mode 2 play multiple notes with a long release and play a single note while the chord is in the release phase, then the chord notes should be cut, but only one of those voises is cut.
Can you describe how you use the sound, when you exsperience the issue? That would be a good idea, if you contact Arturia support, and they need to reproduce the issue.
If you are using the Fact 28 preset with it's programmed Poly 1 Assign mode, then are you also using a hold pedal to hold notes during the playing, and is that perhaps responsible for the behavior you exsperience? Or is it about a random inconsistent behavior with voice stealing?
Does it help on your problem, if you set the preset to in example use 16 or 32 voices instead of 8?