The Knowledge checkbox doesn't work on Problem

In theory, if the Knowledge checkbox in a ServiceNow Problem record is set to true, then a draft knowledge article will be created on resolution of the problem.

In practice, this doesn't happen out of the box, due to a bug (true as of the Washington release).

The solution

The cause is simply an incorrect trigger condition on a business rule on the Problem table called "Problem Create Knowledge".

Out of the box, the condition on which the script runs is:

current.problem_state.changesTo(4) && current.knowledge == true

This condition will never evaluate to true, because there is no problem state with the value of 4. Instead, the correct problem state value is 107:

current.problem_state.changesTo(107) && current.knowledge == true