High leverage can be a powerful tool for traders to magnify their gains, but it also exposes them to significant risks. Market events that can cause high leverage to become problematic are those that can rapidly change market conditions and cause large fluctuations in asset prices. Some examples of such events include:

1. Black Swan events: These are rare and unpredictable events that have a significant impact on the market, such as natural disasters or political upheavals.

2. Economic downturns: Recession or economic slowdowns can lead to a decrease in demand for goods and services, leading to falling prices and losses for traders.

3. Central bank policy changes: Interest rate changes or monetary policy announcements can cause sudden movements in currency markets and affect leveraged positions.

4. Volatile market conditions: Sharp movements in price caused by high trading volume, increased volatility, or sudden news releases can wipe out trading accounts that are heavily leveraged.

5. Margin calls: When the value of the underlying asset falls below a certain threshold, traders may receive a margin call, requiring them to add more funds to their account to maintain their position. Failure to do so can lead to forced liquidation and substantial losses.

In summary, traders must understand the potential impact of these market events and carefully manage their leverage to minimize their risks.