Hi,
I've written the plugin Edge Suite which handles animations in form of OAM files, which are nothing else then ZIPs. I'm using the codex method wp_mkdir_p to create nested directory structures. Turns out some people have problems with it as it just fails. Any clue why that might be? It's really strange, this really common functionality is only being called 4 times in wp core, almost looks like devs know it doesn't work....
Am happy about any hints, as I can't reproduce the errors on my servers and it's therefore really hard to debug it.