Pressing two keys can crash Orpie: single quote (') then down-arrow. I'll attach a patch to fix the crash that I just submitted upstream in case you want to do a -r1 version.
Created attachment 99901 [details, diff] Fix for Orpie 1.4.3 crash
In Portage. Thanks for your work, Samuel. I also added a dependency on ocaml 3.08.4 as it seems to be the only version in Portage able to compile orpie.