Sounds to me like the film was under-exposed. Density in Zone I is more a product of exposure than development, and the fact that you have contrasty highlights suggests that the developer is working as it should and that the working solution was mixed correctly.
Sandy
These are just test exposures. Each frame is of a single tone. Several exposures at zone I for ISO 100, 80, 64, 50, 40, 32, and 25. Then several exposures at zone IX at ISO 100, 80, 64, 50, 40, 32, and 25. All the zone I exposures are blank. The zone IX exposures have reasonable density. The frame numbers and film info did not develop. I shot three rolls of TMX like this. Developed one in Xtol, with no problem and then two in Pyrocat both of which look the same (very thin). If it was under exposed, the farme numbers would still have come out. By the way, all three rolls came from the same 100 foot bulk roll with an expiration sometime next year.
Then, I developed a similar roll of Pan F+ shot the same way except at half the ISO values, also in Pyrocat. It came out fine.
Just as a sanity check, each roll has a few regular scenes taken using the built in camera meter instead of the spot meter. The scenes are also very thin. In doing the second roll, I was very careful about exposure, because I thought I must have screwed it up to make the first roll so thin.
Developer was pyrocat HD in glycol from the Formulary mixed 1:1:100 with distilled water and developed at 70F with inversion agitation at 30 second intervals. No presoak.
I have no doubt that you all have had great success with TMAX 100 and pyrocat, so I'm obviously doing something wrong. I just haven't discovered what it is. TMAX 400 and Pan F+ both came out great. I'm hoping to settle on pyrocat as my sole developer, so I would like to figure out what's going on.
-Dave
[edit] The developer was 3 ml of A, 3 ml of B, and 300 ml of distilled water. And, I would agree that, if it weren't for the fact that the frame numbers didn't even develop, the symptoms are definitely underexposure.