Summary
If MetaTrader 5 stops your backtest with “invalid pointer access in ‘project-file-….mq5’”, your exported EA hit a runtime crash. In plain English: at one specific moment in the backtest, a value used in your strategy (usually SL/TP, ATR, or a variable) became invalid, and MT5 terminated the EA.
This is almost never a login/broker issue. It’s typically a strategy math / build-logic issue that surfaces mid-backtest.
What the error means (plain language)
MT5 tried to execute a trade or management action, but a required value was not usable (for example: stop-loss distance = 0, a negative price level, a missing variable, or a division by zero). When that happens, MT5 can crash the running EA and prints invalid pointer access.
Why it can look “random”
The EA may run fine for hours or days and then suddenly crash. That’s because the invalid value happens only on one specific tick/candle, e.g.:
ATR briefly returns 0 (no data yet / edge case)
your computed SL becomes negative or equals entry
a variable wasn’t set in a branch and is used later
a candle ID points to data that doesn’t exist yet
So the crash is deterministic — it’s just hiding until the exact moment the bad value occurs.
Most frequent reasons for an invalid pointer access
These are the patterns we see most often:
ATR-based SL/TP logic
ATR variable not stored/updated before being used
ATR value becomes 0 (or extremely small), causing SL distance to collapse
Invalid SL/TP calculations
SL/TP becomes 0, negative, or lands on the wrong side of entry
SL/TP distance too small (effectively “invalid stops”)
Using “price fraction” vs “price level” incorrectly
Pips/points conversion issues
Mixing points and pips causes SL/TP to be off by 10x or 100x
Leads to impossible levels or negative distances after math
Variables missing / not initialized
Variable used in a formula before it’s set
A logic branch skips a “set variable” step, but later blocks assume it exists
Division by zero
Any formula where a divisor can become 0 (range width, ATR, spread, etc.)
Negative range / offsets
Range width becomes negative due to wrong subtraction order
Time/window offsets produce invalid values
Unset or invalid Candle ID
Candle ID references data that is not available at that moment (common early in backtest)
Recommended debug workflow (fast, no guessing)
Step 1 — Reproduce it in MT5 Visual Mode
Run the Strategy Tester in Visual Mode and note:
Symbol
Timeframe
Date range
The approximate time/candle where it crashes
Step 2 — Visualize the variables that drive SL/TP/ATR/Offsets
In Profectus, visualize the values that feed your trade execution and management logic:
ATR value (if used)
SL distance / SL price level
TP distance / TP price level
Any range width / offsets / multipliers
Any variables used in Formula blocks that end up in Buy/Sell blocks
Follow this exact guide:
https://docs.profectus.ai/en/articles/12871515-visualizing-variables-on-chart
Step 3 — Watch the values right before the crash
Re-run the backtest and observe the visualized values as you approach the crash candle.
You’re looking for the moment where a value becomes impossible, e.g.:
ATR = 0
SL distance ≤ 0
SL price equals entry price
Range width < 0
A multiplier flips to 0 unexpectedly
Step 4 — Fix by adding “guards” (minimums + validity checks)
Typical fixes:
Ensure the variable is set every candle before it’s used (especially ATR/range variables)
Enforce minimum distances:
SL distance must be > 0
TP distance must be > 0
Prevent negative values:
Use correct subtraction order (high − low, not low − high)
Avoid division by zero:
Add logic to skip calculations when divisor is 0
Confirm correct unit:
If you mean pips, don’t accidentally compute points (or vice versa)
If you can’t guarantee the value is valid on every tick, don’t let the EA use it.
If you’re still stuck: what to send support
Send the following so we can pinpoint it quickly:
Screenshot(s) of the blocks that compute SL/TP/ATR/offsets (Formula + Variables + Buy/Sell/Modify SLTP)
Screenshot showing your visualized variables right before the crash
Exact symbol + timeframe + date range where it crashes
The exact MT5 message: “invalid pointer access in ‘project-file-….mq5’”