To answer some of the questions raised on these other threads here are our requirements (they are not put into the above reproduction because the they add more unnecessary code & I'd rather keep the code nice and simple for you guys to be able to see the bug, but here's what we're actually trying to achieve):
We don't want the grid scroll horizontally (hence the use of forceFit)
We have four columns - one column of a fixed width, all the others should take up the remaining space equally (i.e. the equivalent of what flex does, though note I haven't used flex in the above examples)
Our grid's width is going to be sized by a parent container's layout manager - I don't think this has any bearing on the bug above, but as it's a core requirement I've listed it here
After a little more playing I realise that the simple solution here is to NOT use forceFit (I don't know of any use cases for it now, so perhaps this could be changed to a bug about clearer documentation or deprecating it if it isn't needed).
Instead the correct solution that seems to work is just using flex: 1 on all the columns. So far this has helped achieve the behaviour we required, see http://jsbin.com/ivofav/4/edit for the working example
Again I think it's worth reviewing the docs around forceFit and listing the right use cases for this and highlighting that more often what people want to achieve should be done with "flex" on all the columns instead.