Congrats to you all who finished this challenge.
I've just found some interesting report about the photography bug on a site that I can't mention here.
According to them, it seems that the bugs are mostly happening when a Sim takes a snapshot while an opportunity is opened. All opportunities can be the cause (career, skill, special, but also adventures), and any member of the household is concerned, not only the wanna-be photographer.
What seems to solve the issue is to save, exit game, clear all the caches, then reload. And a properly patched game (*) helps decreasing the frequency. (*: patch all the .exe, not only the base game and the latest EP or SP, like the launcher does)
I'll only test this myself tonight in order to play the challenge 'just on time' tomorrow. I hope this will work and can still help some of you.