usgflex and client/server static ips

hi all

I have recently installed a lot of new usgflex both basic (usgflex100) and more advanced (usgflex200 and 500) to replace the old USG .. both with the new firmware and with the slightly previous ones, I encountered a fairly important problem that check both on lan and vlan interfaces: if I set a static address on any client in the same network environment, the client does not ping the firewall even though the configuration is correct; if I leave the client in dhcp (and obviously I configured dhcp for that interface on the firewall) the pc manages to ping without problems.. if I set the same ip as the static one but with dhcp reservation on the firewall for that specific client, the client ping without problems.. summarizing the problem occurs only if the clients have static ip set on the clients themselves (but this also happens on servers and this could be more problematic).. have you also encountered a similar problem?