jsaddle-warp browser DOS on the Haskell program (stuck on sendTextData)

I'm writing a program which draws many things on a canvas - and have found that if I draw too many things, too fast, then jsaddle-warp will freeze up. It works fine in ghcjs in-browser. A reduced version is below.

module Main where

import Control.Monad (forM_)
import Data.Monoid ((<>))
import Control.Monad.IO.Class (MonadIO(..))
import Control.Concurrent (forkIO)
import Control.Concurrent.MVar (takeMVar, putMVar, newEmptyMVar)
import Control.Lens ((^.))
import Language.Javascript.JSaddle
       (jsg, jsg3, js, js1, jss, fun, valToNumber, syncPoint,
        nextAnimationFrame, runJSM, askJSM, global)
import Language.Javascript.JSaddle.Warp (run, debug)
import Language.Javascript.JSaddle.Run (enableLogging)

main = run 3708 $ do
    enableLogging True
    doc <- jsg "document"
    doc ^. js "body" ^. jss "innerHTML" ("<h1>Kia ora (Hi)</h1>")

    -- Create a haskell function call back for the onclick event
    doc ^. jss "onmousemove" (fun $ \ _ _ [e] -> do
        x <- e ^. js "clientX" >>= valToNumber
        y <- e ^. js "clientY" >>= valToNumber

        forM_ [1..10000] $ \_ ->
            doc ^. js "body" ^. jss "innerHTML" ("<h1>Kia ora (Hi)" <> show (x, y) <> "</h1>")

        liftIO $ print (x, y)
        return ())

Start by running the reduced Main program with jsaddle-warp on port 3708, focusing on the onmousemove callback that performs 10,000 innerHTML updates. Inspect the sendTextData path and compare its behavior with the reported GHCJS browser run. Done means the reduced workload no longer freezes jsaddle-warp while handling rapid canvas or DOM updates.