function unstake(uint256 stakeAmount) external {
  address account = _msgSender();
  require(stakes[era][account] >= stakeAmount, "insufficient balance");
  _payoutRewards();
  _burn(account, stakeAmount);

  uint256 newStakeRSR = (FIX_ONE_256 * totalStakes + (stakeRate - 1)) / stakeRate;
  uint256 rsrAmount = stakeRSR - newStakeRSR;
  stakeRSR = newStakeRSR;

279:  (uint256 index, uint64 availableAt) = pushDraft(account, rsrAmount);
}
function pushDraft(address account, uint256 rsrAmount)
  internal
  returns (uint256 index, uint64 availableAt)
{
  CumulativeDraft[] storage queue = draftQueues[draftEra][account];
  index = queue.length;  // index = 0

  uint192 oldDrafts = index != 0 ? queue[index - 1].drafts : 0; // 0
  uint64 lastAvailableAt = index != 0 ? queue[index - 1].availableAt : 0; // 0
658:  availableAt = uint64(block.timestamp) + unstakingDelay; // T + 1 day

  if (lastAvailableAt > availableAt) {
    availableAt = lastAvailableAt;
  }
  queue.push(CumulativeDraft(uint176(oldDrafts + draftAmount), availableAt));
}
function cancelUnstake(uint256 endId) external {
  uint256 firstId = firstRemainingDraft[draftEra][account];
  CumulativeDraft[] storage queue = draftQueues[draftEra][account];
  if (endId == 0 || firstId >= endId) return;

  require(endId <= queue.length, "index out-of-bounds");

368:  firstRemainingDraft[draftEra][account] = endId;
}
function pushDraft(address account, uint256 rsrAmount)
  internal
  returns (uint256 index, uint64 availableAt)
{
  CumulativeDraft[] storage queue = draftQueues[draftEra][account];
654:  index = queue.length;  // index = 1

  uint192 oldDrafts = index != 0 ? queue[index - 1].drafts : 0; // 0
657:  uint64 lastAvailableAt = index != 0 ? queue[index - 1].availableAt : 0; // T + 1 day
658:  availableAt = uint64(block.timestamp) + unstakingDelay; // T + 1 hour

  if (lastAvailableAt > availableAt) {
    availableAt = lastAvailableAt;
  }
  queue.push(CumulativeDraft(uint176(oldDrafts + draftAmount), availableAt));
}
function pushDraft(address account, uint256 rsrAmount)
  internal
  returns (uint256 index, uint64 availableAt)
{
  CumulativeDraft[] storage queue = draftQueues[draftEra][account];
  index = queue.length;  

  uint192 oldDrafts = index != 0 ? queue[index - 1].drafts : 0; 
  
-  uint64 lastAvailableAt = index != 0 ? queue[index - 1].availableAt : 0; 
+  uint64 lastAvailableAt = index != 0 && firstRemainingDraft[draftEra][account] < index ? queue[index - 1].availableAt : 0; 

  availableAt = uint64(block.timestamp) + unstakingDelay; 

  if (lastAvailableAt > availableAt) {
    availableAt = lastAvailableAt;
  }
  queue.push(CumulativeDraft(uint176(oldDrafts + draftAmount), availableAt));
}
