Thanks, @Citadel535 I get what you're saying about the painful process of tracking down a mod responsible for crashes. I have already been through the "disable recently changed mods" dance without finding a culprit. I've done binary search-like disabling before (never as simple as it sounds) and will probably be doing it again.
In this case, it does not feel like a mod problem: the same collection of mods both works and does not work to load my most recent saves. That said, it doesn't feel like a Vortex problem, either, given that while it arrived with 1.12.0-BETA.2, it stuck around after downgrading to 1.11.7 and then disappeared temporarily after reinstalling 1.12.0-BETA.2 before returning after the system was rebooted (nice to have a workaround, but it sure is fiddly).
Thanks for the "delete pipeline cache" suggestion. I'll test that and see if it helps.