In what appears to be a very old bug, we weren't able to save results to the .qpx xml format from that option in the GUI. Constantly got an unhelpful error message. This is the result of a missing semicolon after a return statement in the save_results() function in src/mainwindow.cpp, which unluckily didn't result in a compiler error. Replacing the semicolon gets it to work.
Accepted. Thanks!
80436ee16923793e0a55bd0bb4d7a16bc5558506
Sweet! :)