Question regarding DRV8860 drtive capacity

Hi,

I am using DRV8860 in my design to drive 8 valves. These valves consume a current of 500mA during pick up and during hold, I can maintain them at 40% (200mA). One strange observation I made about the DRV8860EVM (evam module) is that the module can't drive more than 5 valves in the method of individually activate each valve the bring it to hold before activating the next valve. DRV8860 on my board can drive all 8 valves in this method but not the one on EVM. any specific reason for the behavior? I have tried this on two modules but observed same behavior. Anyone observed this behavior?