Why could the Apri 11th entry be described as the biggest "close call" that the secret annex has had yet.How does Anne frame it in a perspective to improve the image of the Jews?

The annex is burglarized, and when the men go down to frighten away the burglars, they become the burglars for the people who look through the windows with a flashlight. The police come, the annex members are frightened, and it is pretty much a few "days" of chaos.

I am unsure what you mean about improving the "image of the Jews'?