I think something's gone wrong with the triangle generation / solving layer, where regenerating the geometry takes forever. This happened very suddenly to a file I was working on; attached.

It's something to do with the g011-holes or g012-extrude. If I try to export with g011-holes selected, it exports almost immediately. If I try to export with g012-extrude selected, it takes O(minutes), sometimes O(tens of minutes) --- I only realised it hadn't hung when I left the machine for a while and came to back find the save complete.

actionrider2.zip

This is with version 3.1~b4625657, Debian Linux amd64.