Modifiers matching trouble:

• internal,
• small,
• unexpected,
• unforeseen,
• psychological,
• mechanical,
• serious,
• everyday,
• fatal,
• sexual,
• financial,
• real,
• mental,
• temporary,
• economic,
• experienced,
• environmental,
• undesirable,
• political,
• major,
• technical,

Simple categories matching unforeseen:

• cataclysm,
• circumstances,
• event,
• catastrophe,
• misfortune,
• incident,
• case,
• force,
• trouble,
• occurrence,
• weather,
• development,
• situation,
• disturbance,
• hazard,
• eventuality,
• problem,
• expenditure,
• condition,
• work,
• expense,
• charge,
• disaster,
• thing,
• emergency,
• circumstance,
• calamity,
• accident,
• setback,
• shock,
• adversity,
• contingency,
• happening,
• difficulty,
• consequence,
• crisis,