Thank you for trying. When you initialise patch you have three slots filled for modulation matrix so it assigns it to modulation slot #4, and it does it even when you are on an another modulation slot which is annoying. And to see this is a bug, even after you assigned a source to modulation #4, this shortcut always assigns it to the same spot, as I've said it doesn't check focused slot for the modulation source. Also I tried some factory patches, which has 9 slots filled, and it automatically assigns it to number 10. So the logic is true that it assigns it to the first empty slot, but it keeps assigning to the same spot, even when you assigned a thing there, so it doesnt look for empty slot. Anyway it is clearly a bug. I am glad someone verified this. I will send Sequential an e-mail, which I should already have, but I thought they were already looking here.