[Therion] No passage walls converting .plt to .lox

Hello, I have a Compass .plt file which I am able to display with Loch. I happily see station names and passage walls. I'm trying to generate a .lox file to display with CaveView on the web. CaveView needs .lox format. To do this, I import the .plt in Therion then export the lox model enabling all features (walls, splays, etc.), but I get no walls in the final file. I tried to generate a .lox model from a test .th file written by hand and I was able to get all the features. Am I missing something? Thanks, Marco