Error in receiving data with synchronized 5 USRP2 boards

[Yikai]

I am trying to synchronize 5 USRP2 boards and receive data. It works when I choose 'Now' in 'apply timestamp' of 'niUSRP Set Time'. However, when I switch to 'Next Timebase Edge', why doesn't it work? It always comes to be the errer of 'A stream command was issued in the past'. Is it caused by hardware or software? How to fix it?

The test file is in the attachment.

I am also very sure that I have synchronized the boards with a signal generator and a waveform generator. The signal generator generates a 10 MHz signal with amplitude of -5.4 dBm. The generated signal then goes through an amplifier to have a peak-to-peak amplitude from 2.5V to 3V. After that, the output is connected to REF CLOCK ports of the receiver boards through a splitter. The waveform generator creates a square wave with Vpp = 5V, Vp = 5V and frequency of 1 Hz. It connects to PPS IN ports of the receiver boards via a splitter. All cables have the same length.

[ErikL]

The challenge is likely the string input at the top of the VI where you select "on next time base edge. Use a comma separated list with each device that has external inputs to PPS. I.e. the first ip address in the list is device 0. So if I had an ip list of 4 boards and the first and third where attached with an external clock (with the other two MIMO cable teathered) then the string would say 0,2 .