As I recall, the old 4000 (not 4000B) series ICs were quite sensitive to latchup and ESD damage compared to more modern parts. They're probably fairly hard to get ahold of in 2020. You could try a standard CD4001B for example, cheap and easily socketed for replacement.
Charging a small capacitor to high voltage and discharging it through the part with a low value or no capacitor may be able to demonstrate the damage. You can start with the usual human body model and make it less friendly (lower resistance, more capacitance, higher voltage) as necessary.
For demonstrating damage, I suggest a SPDT switch to a gate input with a high value resistor in series (maybe 22M or more), and the output driving an LED, so that any damage that causes somewhat increased leakage to either supply rail will be evident. Add a series resistor to the Vdd so latchup doesn't kill the chip if you want to zap it with the power applied.
Note that the ESD discharge that is guaranteed safe may be considerably less than what is required to typically cause measurable damage.