Trading Bot Bug Fixing — Diagnose and Repair Your EA or Bot Fast
Your robot is rejecting orders, crashing, or not doing what the code says? We reproduce the problem, find the root cause and fix it with minimal, reviewable changes.
Trading bot bug fixing is diagnosing why an Expert Advisor or script misbehaves, such as failed or rejected orders, wrong lot sizes, logic errors, crashes or slow execution, and repairing it. ExpertNevees fixes MQL4, MQL5, PineScript and Python bots, typically in 1–3 days, using minimal targeted changes and explaining the root cause so it does not return.
Typical Problems and Their Usual Causes
| Symptom | Frequent causes | Typical fix |
|---|---|---|
| Orders rejected with invalid stops | Stop-loss or take-profit closer than the broker’s minimum stop level, or not normalized to the symbol’s digits | Read the symbol’s stops level, normalize prices, adjust distances |
| Invalid volume | Lot size outside minimum, maximum or step | Normalize volume to the symbol’s step and limits |
| EA opens trades twice | Logic runs on every tick without a new-bar or position check | Add new-bar detection and position check by magic number |
| Works in tester, not live | Different spread, filling mode, symbol names, or look-ahead in the test | Check filling policy, symbol mapping and costs |
| Indicator repaints | Use of unconfirmed current bar or future data | Evaluate on confirmed bars only |
| Array out of range / zero divide | Missing data checks, empty history, unguarded divisions | Validate array sizes and denominators |
| Terminal freezes or EA is slow | Heavy loops on every tick, repeated history copies | Cache, compute on new bars and optimize loops |
A Typical Fix: Guarding History Access in MQL5
// BEFORE: crashes with "array out of range" when fewer than 3 bars are loaded
// MqlRates rates[];
// CopyRates(_Symbol, PERIOD_CURRENT, 0, 3, rates);
// double prev2 = rates[2].close;
// AFTER: verify how many bars were actually copied before indexing
MqlRates rates[];
ArraySetAsSeries(rates, true);
if(CopyRates(_Symbol, PERIOD_CURRENT, 0, 3, rates) != 3)
{
PrintFormat("Not enough history yet (error %d)", GetLastError());
return; // skip this tick instead of crashing
}
double prev2 = rates[2].close; // safe nowMany “mysterious” bugs are unchecked return values. We add the checks and logging that make the next failure obvious instead of silent.
How a Bug Fix Works
Describe the problem
Send the code, the symptoms, the Experts and Journal log lines, and your platform and broker.
Reproduce
We reproduce it in the Strategy Tester or on a demo account, because a bug we can see is a bug we can fix.
Find the root cause
We trace it to the exact line and condition, and tell you why it happens.
Minimal fix
The smallest change that solves the problem is applied and tested, so that the rest of your code stays as it is.
Delivery with explanation
You receive the fixed source, a summary of changes and a regression test result.
Information That Speeds Up the Fix
- ●The source code (or the compiled file, if you do not have source, to assess the options).
- ●Exact error messages and the relevant lines from the Experts and Journal tabs.
- ●Platform and version, broker name, account type (hedging or netting), symbol and timeframe.
- ●What it should do versus what it does, with an example time when it went wrong.
What We Can and Cannot Do
- ●We fix defects and extend code we are given the right to modify.
- ●We do not remove licensing, protection or copy-protection from other people’s software.
- ●Fixing a bug does not make a losing strategy profitable. If the strategy itself is the problem, see Strategy Analysis.
Delivery, Support & Guarantee
Timelines are indicative. The exact price and delivery date are confirmed in writing before work starts, with no hidden costs. Payment: 50% advance, 50% after your approval (USDT or bank wire).
Frequently Asked Questions
How fast can you fix my EA?
Most bugs are fixed in 1–3 days. Simple issues can be quicker, and deep logic problems or large optimizations can take longer. We give an estimate after seeing the code and symptoms.
Can you fix an EA if I only have the compiled .ex4 or .ex5?
Without source code we generally cannot modify the program. We can still analyse its behaviour and advise. If you have the source, send it.
Why does my EA work in the tester but fail live?
Common reasons are different spread and slippage, filling mode, symbol naming, stop-level constraints and look-ahead in the test. We diagnose which applies.
Can you add a new feature to my existing EA?
Yes, such as trailing stops, news filters, notifications or risk management. For large additions see Expert Advisor Development and Capital & Risk Management.
Will you rewrite my whole code?
No. We prefer minimal, targeted changes you can review. A rewrite is suggested only when the structure makes reliable fixing impractical, and only with your agreement.
Can you fix my Python bot or PineScript?
Yes. We debug MQL4, MQL5, PineScript and Python. See also Custom Indicator Development.
Official Documentation & Sources
- MQL5 Reference — Trade Return CodesMQL5.comView Docs ↗
Stop Losing Time to a Misbehaving Bot
Send the code and the symptoms. We confirm what is wrong and how long the fix takes.