Problem type checking with natural transformation in record type

Main.purs

module Main where

import Prelude
import Effect (Effect)
import Data.Foldable (fold)
import TryPureScript (h1, text, render)

data Nat m n = Nat (m ~> n)

data NatR m n = NatR { nat :: (m ~> n) }

morphS :: forall m n. Monad m => Monad n => (m ~> n) -> m Unit -> n Unit
morphS t fm = t fm

-- useR :: forall m n. Monad m => Monad n =>  NatR m n -> m Unit -> n Unit
-- useR (NatR { nat }) x = morphS nat x -- Error!
-- Error: Could not match type a4 with a1 
--   a4 rigid type variable bound at line 17, column 34-54...
-- Stays at line 17 even if I move the code around.
-- Actually it's also the same location in my local code base... Wat?   

useR' :: forall m n. Monad m => Monad n =>  NatR m n -> m Unit -> n Unit
useR' (NatR h) x = morphS h.nat x -- Works

useR'' :: forall m n. Monad m => Monad n =>  NatR m n -> m Unit -> n Unit
useR'' (NatR h) = morphS h.nat -- Pointfree also works

main :: Effect Unit
main =
    render $ fold
      [ h1 (text "Try natural transformation in records!")
      ]