Cubase freeze on Mac for few seconds, then recovered

Since installed C11 suddenly freeze for 30 seconds or so when I am in Play or playing my MIDI keyboard. I am on a MAC mini i7, 16 Mb of RAM on OS Catalina. Sometimes the beachball appears, sometimes it not. When recovers, all the notes I was playing sounds like nothing happened… Others MAC windows seems to works fine, and I also checked with the Monitor App, and nothing seems to be in a critical limit, not the memory, nor the disk. I wonder if the USB Licenser has something to do… Thanks for the help.