LTC4020 hot swap battery

Hello,

I want to use LTC4020 in my project to charge a lead acid battery.

I found a problem and do not know how to solve it, if I turn it off during operation and charging the battery, then the voltage on Vout jumps to > 40 volts, my output capacitor exploded. Is this normal LTC4020 operation or do I have a problem?

Kind Regards
Vladimir