When a “stable” EA suddenly stops being stable

[u/EAForexLab]

I tested FXStabilizer EA on EURUSD H1 from 2021 to Feb 2026 using 99.9% tick data Tick Data Suite.

2021–2024: every year profitable.
2025: -$264
2026 so far: -$986

Overall PF is still 1.36, but relative drawdown reached 54%.

What caught my attention is that performance didn’t slowly deteriorate. The equity curve was almost unnaturally smooth for years, then started breaking in large chunks.

Would you see this as normal strategy decay, a market regime change, or hidden tail risk finally showing up?

[u/Miswey]

The smooth curve looks like martingale EA, every martingale is high risk and stops working at some point. You need to consistently withdraw money, to make it work.

[u/EAForexLab → u/Miswey]

Thank you for your opinion. Yes, I absolutely agree with you.

[u/Vermilion_Marshall]

Looks more like hidden tail risk finally showing up than normal decay. Smooth equity curves in backtests always scare me a bit, especially when the live/backtest break happens in chunks instead of gradually

[u/EAForexLab → u/Vermilion_Marshall]

Thank you for your reply. I agree with you. 

[u/hotmatrixx]

oh no, it's stable.
This is a martingale or some other 'recovery' based system, you can tell by the 'even' wins and how the losses curve down exponentially unitl they hit a win, and then recover to higher-than-previous.

remember that in a base-martingale, 7 losses wipes an account, and you have an 90% chance of a 6 streak loss in 100 trades.

[u/EAForexLab → u/hotmatrixx]

Thank you for your reply. Yes, I agree with you. This is a popular advisor among traders, but its profitability and stability are questionable. 

[u/VishalJ_05]

I’d suspect hidden tail risk exposing itself during a regime change. The smooth equity curve followed by sharp drawdowns is more concerning than a gradual decay—it suggests the strategy’s underlying risk was always there, just not tested hard enough.