So, I've been doing missions for Caeda Celeste at Chitagupta.
If I select "Try to spark a conversation with Caeda Celeste" followed by "So we're on friendly terms now?" I get a hullmod item in my inventory. If I'm fast, I can right-click on it and learn it, after which point everything seems to be fine. If I'm not quite so quick, it tries to bring up the tooltip for the hullmodspec item, and Starsector crashes with "Fatal: Format specifier 's' Check starsector.log for more info."
There is nothing in the log - no stack trace, no error report, just a silent end.