There are two ways to gain temporary insanity cards in WFRP, but the interactions between them aren't completely clear.
Insanity rules when Willpower is distressed and the character gains stress:
1) Check if the character has already gained a temporary insanity in this encounter.
2) IF the character has NOT gained an insanity this encounter, test to see if they gain one now.
3) IF the characters HAS already gained an insanity this encounter, it grows deeper by placing one tracking token on it!
No Problem!
The "Strain and Insanity" rules
1) Each time a strained character gains a point of stress or fatigue, he gains a fresh insanity card.
2) Each time a strained character gains a point of stress or fatigue, they also place one tracking token on the most recent insanity gained.
My inferences on the interactions between these conditions:
a) Strain will never cause more than one tracking token to be placed on an insanity, because it always generates a fresh insanity card when it triggers.
b) If a strained character ALSO has distressed Willpower, both effects will trigger. They will gain a new insanity and two tokens will be placed on it. (You could argue timing on this, but meh.)
c) A character who has just become distressed / strained does not risk insanity, they have to already be strained / distressed before gaining a fatigue or stress token will trigger a breakdown.
Does this match up with your interpretations?