Unwritten rules

Unknown procedures

Unwritten rules (synonyms: Unspoken rules) are behavioral constraints imposed in organizations or societies that are not typically voiced or written down. They usually exist in unspoken and unwritten format because they form a part of the logical argument or course of action implied by tacit assumptions. Examples involving unspoken rules include unwritten and unofficial organizational hierarchies, organizational culture, and acceptable behavioral norms governing interactions between organizational members. These rules typically align with the behaviors of the local majority group and seem normal to them, but can be obscure, invisible, and exclusionary to minority groups.

Source: Wikipedia

When it gets to be your turn, they change the rules.
(F) Fuzzy exceptional problems