I finally remembered to report a bug I hit a couple weeks ago while I was offline. I was using 0.99J1 at the time.
The problem is that openxcom crashes with a "UFO (Mapblock CSHOUSE_01) could not be placed on the map" error, as shown in the screenshot.
I've attached a savefile - if I loaded it and let the ship reach the mission (takes a few seconds), the bug triggered. I don't know whether this is still reproducible in 0.99J4. Also the log doesn't seem to include any relevant information; I wonder if a debug build of OpenXcomEx would help in that regard.
(As a side note, I'm grateful to the openxcom devs for including a suggestion to turn on save scumming, so that the map generator can create the map with a different PRNG seed and not crash
)