I thougt you are right, because after installing of second printer the values of usb serial were same. I set the port values in Repetier "/var/lib/klipper/sockets/V1" and "/var/lib/klipper/sockets/V2". In Klipper config is serial "/dev/serial/by-path/platform-fd500000.pcie-pci-0000:01:00.0-usb-0:1.3:1.0-port0" for V1 and /dev/serial/by-path/platform-fd500000.pcie-pci-0000:01:00.0-usb-0:1.4:1.0-port0 for V2. It looked fine, both printer were connected, both started to print. After a while (after initial gcode) one of the printer ended with error.
Where can I check unix socket please