pitfall

A potential, unsuspected, hidden problem, hazard, or danger that is easily encountered but not immediately obvious.

It's usually a simple task, but you should know the pitfalls before you attempt it yourself.

A type of trap consisting of a concealed pit in the ground, which the victim is supposed to fall into and not be able to get out from.

An antipattern.

Subsidence below ground in a mine, which can cause the ground level above to drop.

This pitfall, beginning in February and finishing in May, resulted in a drop of about 3 ft. in the platform level; during this period it was necessary to level the track three times weekly, and impose a service slack of 15 m.p.h. The subsidence appears now to have finished, and normal speed is once again permitted.