Category: Strategy Testing & Analysis | Last Updated: April 2026

Who this article is for. Playback (Market Replay) is an optional tool for hands-on clients who want to observe strategy behavior over historical data. Most Vector clients don't need to use it — running the strategy live in your prop firm SIM account gives the most accurate picture of how it behaves. If you're not deliberately experimenting with playback, this article likely doesn't apply to your setup.

If you are using playback and running into issues, here are the common causes and what to check.

Strategy Disables After One Trade in Playback

Common causes:

• Session boundary detection. The strategy may disable when it detects what it thinks is a session boundary, and playback can sometimes trigger that detection unexpectedly depending on the data range.
• Insufficient historical data. Playback needs enough lookback data to fully calculate the strategy's indicators. If the replay window is too short, the strategy may not have enough information to continue firing after the first trade.

Strategy Won't Fire at All in Playback

Quick checklist:

• Correct instrument and timeframe — match what the Settings Spreadsheet specifies for the strategy
• Strategy is enabled — verify the checkbox in the Strategies tab is checked after you added it
• Playback date range covers active trading hours — if your replay window falls entirely on a weekend or overnight-only period, nothing will fire
• Strategy version in playback is the current one — if you've been upgrading, make sure the playback is running the same version you want to evaluate

Context: Playback vs. Live Behavior

Playback is generally reliable and gives a reasonable read on how a strategy performs — in most cases, the results line up well with what you'd see live. That said, because playback replays historical tick data through NinjaTrader's replay engine, there are occasional situations where it doesn't capture every detail the same way a live session would (session boundary edge cases, very thin-volume moments, etc.).

Live or forward-testing on your SIM account is still the most accurate way to observe how a strategy actually behaves in current market conditions — but for most hands-on exploration, playback results are trustworthy as a reasonable proxy.

Bottom Line

Playback is a useful tool for hands-on clients who want to explore a strategy's behavior over historical data. For most sessions you run, the results are reliable. If a strategy disables early or doesn't fire at all in playback, check the date range, data coverage, and version first — and keep in mind that live or forward-testing in SIM is always the most accurate reference point.