Decay is normal; the question is the threshold
A drawdown is not evidence of a broken edge. A strategy with a genuine 55% win rate will produce losing streaks routinely, and a system that ejects leaders on every bad week is guaranteed to sell exactly the traders it should hold.
The threshold problem is therefore two-sided. Too tight and you churn, paying fees to chase the recent past. Too loose and you keep funding a decayed edge while it grinds the basket down. Probation exists to create a middle state instead of forcing a binary.