Problem with a nixie clock
The manual says that booster generates 170V DC, when datasheet for IC HV5812 specced for 90V absolute max. The driver IC is killed by design. There is no means in booster schematics to limit the voltage to any predictable value (no zener of voltage feedback).

Old russian equivalent driver K155id1 is BJT based and specced to 60V max, but has a voltage limiting zener per each output 0.5 mA max, so it could survive better. Possibly the replacement with contemporary device was done with mistake of not adding a single 80V zener to booster.