Back in the early 90s, a Herc that I was on, had to return to Southampton low level, because, as I recall the FE saying, there was a LOX leek. He explained that the LOX was located under the cockpit. I may have got this wrong, but I seem to recall him saying too, that an incident happened (over Australia?) in which a transporter lost its cockpit section due to the LOX cooking off. I may have got some of that wrong, he may have been spinning a yarn. But I found this picture - I'm not sure if there's any credible connection.
https://commons.m.wikimedia.org/wiki/File:LOX_servicing.jpg