Good news: A second roll of TMY2 batch 0167 worked great! I changed two things:
* All non-developer liquids (presoak, stop, fix, wash) were at the higher temperature of 22-24C (instead of 18-19C).
* I mixed fresh TF-4 fixer.
Unlike the last try, the following occurred as expected:
* Fixer poured out magenta (instead of clear).
* Wash-water poured out magenta.
* Film had no residual magenta colouration.
* Density-curve is perfect, as shown below:
The first symptom that changed is the colouration of the fixer, so perhaps old TF-4 fixer fixes not only the image but also the magenta dye? The old fixer was clear (not yellow) and had a clearing-time of 60 seconds, so I thought it was fine. But it had 51 rolls run thru it, and the instructions said it is good for 28. Oops. Could old fixer partly bleach the silver image? It's hard to imagine why densities would be low.