Cisco Switching/Routing :: SG 300-10 / All Pings Timing Out After 2 Responses?

I have recently installed a new Cisco SG 300-10 switch--running in layer 3 mode--to function as a basic router for a new subnet installed at one of my company sites. When we attempt to ping devices on the 15.120.204.0 subnet from the 230.20.1.0 subnet, each device gives 2 responses and then times out continuously after that. If we wait long enough (thus far, an undetermined period of time) and reattempt to ping the same devices, the same thing occurs. Otherwise, we get nothing but timeouts. This occurs regardless of where we connect in the 230.20.1.0 subnet including VLAN1 on the SG 300-10. However, if we connect into VLAN 2 on the switch and assign a static IP, those same devices respond continuously. I was thinking that this must be a security setting of some kind but I'm unable to locate anything in the SG 300-10 that would appear to cause this.