On my topics that contain spoilers with images inside of them, the images have moved outside of the spoiler. However, this is only on the OP of the topics, not on any of my other posts. Another interesting thing is that it only occurred with images, and not with text.
This is unfortunately due to a problem with the way BBCode works on IPB. For some reason a lot of BBCode heavy posts have broken BBCode that IPB parses correctly but shouldn't. There is no magic solution for this unfortunately, after launch of the new site I'll be spending some time manually repairing broken topics. If you see it now you're welcome to PM me the topic you've seen it in so that I can add it to my list to be fixed at launch. Sorry for the inconvenience!
Spoilers with images