Yesterday, wife gets a call at 9AM telling her that the floor guy would be at our house at 11AM. He shows up at 12:45. Asks which of the dozens of 1/8"-1/4" gaps we want him to fix. She says "Umm... all of them?" He says he's "not going to fix them all." So, he works on three or four of them. Then leaves, saying he'll be back on Thursday to do a few more. Leaves our house covered in sawdust and wood particles. Didn't bother covering any furniture.
I suspect the builder is probably twisting the floor-guy's arm to do this, because he obviously is not thrilled about it.
On the other hand, it looks like he's fixing the gaps by:
1. Sawing-out the existing boards around the gap.
2. Cutting new boards which are slightly wider than the old boards. ?
3. Banging them into place.
I wonder about the permanence of this fix. I don't see any nail holes on top of the new boards, so I suspect they are either glued down, held in place by friction and pixie dust, or he did a truly expert job of filling the nail holes.

Can’t you demand the entire floor is replaced? Or do the repairs look OK?
Settlement is normal, wooden floors are popular, so this can’t be an unusual problem can it? The builder must have seen this before.
So it’s established that the floor boards didn’t shrink, the house has settled and caused the gaps… so what you really need is a giant clamp to squeeze it back together!
the four he’s done so far are a nice proof of concept, but he really needs to do about 20 more of them. they look ok, so far. i think he needs to put another coat of finish on – they’re still a little lighter than the surrounding wood.
i’d love a whole new floor. but i don’t think we’re gonna get it. it’d probably be $15000 or more, and i can’t see the builder going for that.
giant clamp … i like the sound of that!
Giant clamp in Belgium.
that’s awesome.