Hi JerryChang,
the issue can be observered also when we just capture and stream the images over the network. So the load is low. I recorded small image sequences of our test case. One using the mailbox mode, the other one using the fifo mode. Both at only 4 fps. Maybe you can have a look on it, to understand the problem. You can find them here: [url]Web-Trust-Center-Anmeldung
One can see that one of the three cameras is completly out-of-sync. Which one seems to be random. The other two are nearly in sync, but there are also single frames that are wrong.