I see three possible sources of your problem. First, you've got a bad batch of film and it's a lot slower than even the 2/3 stop reduction you're already giving it -- have you tested for speed, checked your shadows? Second, you've got a bad batch of film that simply doesn't have the D-max you need. Or, third, Maco up100 just doesn't like the Efke pyrocat -- try it in another developer (which would also help with the second possibility).
If the film works okay with another developer (HC-110 at high dilution would be my choice, because it seems to work with everything), then it's just that film and developer not getting along; if it still has poor D-max then it's a film problem -- and if you have no shadow detail either way, but get good highlight density in the other dev, it's lower speed and you need to downrate further (though you shouldn't have to go below EI 50 with an ISO 100 rated film, unless in something like Microdol-X stock solution).