After updating react-dom to version 17 the build now includes Array.fill() which isn't supported by ie11 without polyfilling. Coming from this line. Tested with just the default cra production build to make sure it wasn't a problem with my webpack config and the same issue.

https://github.com/facebook/react/blob/96ac799eace5d989de3b4f80e6414e94a08ff77a/packages/react-reconciler/src/ReactFiberLane.js#L671

Tested using CRA on version 16.9.8 of react and react-dom which works with the production build for ie11. 


let lanes = noLongerPendingLanes;
  while (lanes > 0) {
    const index = pickArbitraryLaneIndex(lanes);
    const lane = 1 << index;
    entanglements[index] = NoLanes;
    eventTimes[index] = NoTimestamp;
    expirationTimes[index] = NoTimestamp;
    lanes &= ~lane;
  }
}
export function markRootEntangled(root: FiberRoot, entangledLanes: Lanes) {
  root.entangledLanes |= entangledLanes;
  const entanglements = root.entanglements;
  let lanes = entangledLanes;
  while (lanes > 0) {
    const index = pickArbitraryLaneIndex(lanes);
    const lane = 1 << index;
    entanglements[index] |= entangledLanes;
    lanes &= ~lane;
  }
}
export function getBumpedLaneForHydration(
  root: FiberRoot,
  renderLanes: Lanes,
): Lane {
  getHighestPriorityLanes(renderLanes);
  const highestLanePriority = return_highestLanePriority;
  let lane;
  switch (highestLanePriority) {
    case SyncLanePriority: