The current capacity of the motor driver board is also a potential limiting factor. Note that solenoid throws are peaky, and most power supplies can handle significant overcurrent for short durations. I would also be surprised if DCC++EX will shut down the outputs based on a single over-current reading. Hopefully, they would wait for multiple consecutive (or averaged) readings over the trip limit. Over-current damage to electronics (the motor driver IC) is almost always from the power dissipated as heat, and heat takes time to build up (and cool down).