From Mark Smith (@surfncircuits):

Eliminating Nixie Tube Cathode Poisoning, Bi-Quinary Digit Ghosting, and Heavily Oxidized Leads

Bi-quinary driven Nixie tubes have nice features by requiring a low bias current and minimized shift registers, but also are sensitive to digit ghosting and require a good level of cathode poison elimination. With the procedures and circuit tricks described above, this was successful for the ETA Nixie Tube Clocks. Good luck with your testing. Let me know if you have any comments or your own improvements.