How does Replikanto handle errors if a trade closes in Replikanto but doesn't reflect on the broker?

This article explains what happens when a trade is closed (or opened) in Replikanto but the broker account does not end up in the same state, how Replikanto tells you about it, and what Follower Guard can do about it automatically.

How Replikanto signals the problem

Replikanto does not silently assume that a copied order reached the broker. Whenever the leader's or follower's position changes, it compares the two accounts and shows the follower's state as a colored circle:

Out of sync (yellow) — the follower's position does not match the leader's, but the follower still receives trades.
On (green) — connected and in sync.
Off (gray) — not connected; no trades are copied.
Disarmed (red) — stopped by Follower Guard; no trades are copied.

So if a trade closes on the leader but the follower's broker position stays open, the follower turns yellow. The synchronization check runs only on enabled (On) follower accounts, and only when leader or follower positions change.

Common causes of a mismatch with the broker

The order was not filled — the leader's order filled but the follower's order did not, or filled only partially, leaving different position sizes.
The close did not reach the broker — a position closed on the leader fails to close on the follower, so the follower keeps an open position while the leader is flat.
The broker rejected the order, or the order could not be submitted at all.
The instrument does not support order updates at that exchange or broker, or the order had not been submitted yet when the change was sent.
Manual trading on either account — opening, closing or resizing a position by hand makes the accounts diverge.
Connectivity or platform issues — disconnections, restarts or delays can cause missed or late execution.
A stale position on a Rithmic account (mitigated in 1.7.0.0) — NinjaTrader still shows a position the broker already closed, or misses a fill, because Rithmic's position updates do not always arrive in step with fills. Closing that phantom position can open an inverted one. Starting with Replikanto 1.7.0.0, Replikanto re-reads the real position from Rithmic, with no order sent, before it flattens a follower or Follower Guard acts, and corrects NinjaTrader's position on its own shortly after a fill that has no position update. See Rithmic phantom positions: NinjaTrader shows a position already closed.

What to do when it happens

Compare the accounts side by side — identify exactly which positions or orders differ in direction, size, entry price or open orders.
Identify the cause — a rejected or unfilled order, a manual trade, or a connectivity problem each call for a different fix.
Correct the position — enter the missing position manually, close one side if the accounts are on opposite sides, or adjust the follower's size after a partial fill. You can also use the follower Flatten button to bring the follower back to flat.
Monitor the next few trades to confirm that synchronization was restored.

Letting Follower Guard react for you

Follower Guard exists precisely for these situations: it can disarm or flatten a follower account automatically instead of leaving the mismatch open. Its actions include:

Acting when the follower's order is not filled after the leader's order filled, waiting a delay you define (5 seconds by default).
Acting when the follower becomes out of sync with the leader, after a configurable time — this action flattens the follower account.
From version 1.5.3+, flattening the follower if it opens a position opposite to the one it should have.
Flattening after a configurable time when the broker rejected the order, when Replikanto was unable to submit the order, or when the exchange/broker does not support order updates for that instrument.

On Rithmic accounts, starting with Replikanto 1.7.0.0, Follower Guard re-reads the real position from Rithmic before it treats a follower as out of sync and before it flattens it, so a stale position in NinjaTrader no longer triggers a false flatten.

Follower Guard is configured from the Replikanto Properties menu, in the Follower Guard group. It can also email you whenever a follower is disarmed, which is especially useful when you run trades unattended. That email requires NinjaTrader to be set up to send mail first: in NinjaTrader go to Tools > Options > General, fill in the "Email log alert messages to" field, and configure a mail account under Share Services.

Why you should not ignore a yellow follower

Unexpected losses — if the leader closes a winning position and the follower stays open, the follower can give back gains or take a loss the leader never had.
Missed opportunities — a follower that failed to enter misses trades the leader took.
Amplified drawdowns — in volatile markets a small positional mismatch can produce very different outcomes.

Prevention

Enable Follower Guard so mismatches are handled automatically.
Avoid manual trades on leader or follower accounts.
Keep enough margin on follower accounts — low margin is a common cause of failed fills.
Check that both platforms are running and connected, especially after updates or network problems.
Compare leader and follower positions periodically, even with no yellow indicator.