The rulebook states the following about rule conflicts:

The Golden Rule
If 2 or more rules ever conflict, the rule on the card always takes precedence over the general rules in this rulebook.
(Page 7)

This means:

• If an Event card (which is a type of card) specifies an effect that conflicts with another card or ability, the specific rule on the card takes precedence over the general rules in the rulebook.
• The Golden Rule does not distinguish between beneficial or detrimental effects; it simply states that the card's rule overrides the rulebook.

However, the rulebook does not explicitly state that Event cards override other cards or abilities—only that "the rule on the card" takes precedence over the rulebook. If the conflict is between two cards (for example, an Event card and an Investigator's ability card), the rulebook does not specify which card takes precedence.

Summary

• If the conflict is between an Event card and a rule in the rulebook, the Event card takes precedence, regardless of whether it is detrimental to the Investigators.
• If the conflict is between an Event card and another card or ability, the rulebook does not specify which takes precedence.

Source: Page 7 (The Golden Rule)

Source: Core Rules (pp. 11, 14, 16, 2, 7)