Reproduction steps:
Open AOE2DE unmodified dat file
Navigate to effects tab
Create or modify any effect command, e.g. 3 - Upgrade unit
Select unit 1509 from the dropdown box - triggers unhandled exception
This occurs at many higher IDs with no obvious pattern. 1509 happens to be the highest ID of Techs at present but this seems coincidental. Unit 1508 appears identical except for internal name.
If the unit is selected by typing the id and hitting enter, it will not trigger the error, but advancing and going back on the dropdown menu at this point can cause a hard crash.