Hi there @Christiaan_Huizer 
!
I’m no FormulaMap() expert (still learning about this versatile formula 
), and I haven’t been using Slice() a lot but I just think the Nth() are not necessary in your Slice() formula.
As when using Slice(), you’re already indicating a position where it should start and end, making Nth() useless (I think ). I was still able to make the formula work using Slice() + Nth() (see the field Failure) but I’m pretty sure some part are redundant (feels like it, at least 
)
Anyway, I did play a little bit with your doc (after copying it 
) and ended up with this formula :
Sequence(1,thisRow.thelist.Count()-1).FormulaMap(thisRow.thelist.Slice(CurrentValue,CurrentValue+1))
Which seems to work .
I did try another approach (see List() 1 + 2 ) as your post made me think about something I asked some time ago and kind of took as an inspiration the answer Paul gave me .