I don’t think that the number of devices you are using with it would affect it as I use a smartphone iPad and many other devices to monitor my cameras and I never have had a problem.
The only other thing I can think of is to turn up the sensitivity for motion detection on your cameras. I found that when my motion sensitivity was lower, it didn’t register it as an event until the motion (usually a person) was leaving which would leave me with only 2-3 seconds of motion. When the sensitivity is higher it picks up motion quicker and started recording quicker.
If still nothing is working, I would recommend contacting the awesome support team at