Where does the ESL current flow when all AC side switching devices are off and the “Icapbank” current is negative? There is no available current path.
With a non-ideal switch the continuous inductor current will flow through the off resistance of the device leading to large voltage. You can model this by a “large” resistance in parallel with your AC side switches. This will slow the simulation down. Alternatively the ESL could have an equivalent parallel resistance, if that models something physical in your capacitor model.