WP7608: Module connecting & then disconnecting after fixed interval of time

We have designed a custom board using a WP7608 module. From our SoC USB port, we have connected 1:4 USB hub (Hub 1) & connected another 1:4 USB hub (Hub 2) to this Hub 1. WP7608 module is connected to one of the four ports of this Hub 2. The path is like:
SoC----> Hub 1----> Hub 2----> WP7608.
Also the UART1 (Tx & Rx pin only) of WP7608 is connected to UART of SoC.

Now, after board is powered ON, the WP7608 module is getting detected and can be seen through ‘lsusb’ command. It remains connected for 125 to 130 secs and then disconnects (No showing in lsusb), remains disconnected for 45 to 50 secs and again connects. This cycle is repeating indefinitely.

We have removed everything connected to RESET_IN_N (pin no.11) from outside.Now its open. We have pulled down PWR_ON_N (pin no.59) through 10 KOhm resistor. We checked our supply, its OK. Even provided supply to module from outside.
We have connected MangOH red board to second port of Hub 2 (module is connected to 1st port of Hub 2), MangOH red is working fine.
Following observations were made during these cycles:
i) We can not give any AT command when the module is connected for 125 to 130 Secs.
ii) VGPIO (pin no.45) gives constant 1.8V during this cycle.
iii) RESET_OUT_N (pin no.46) becomes low for few ‘msec’ when module disconnects.
iv) SAFE_PWR_REMOVE(pin no.152) goes High after module disconnects, and goes low 6 to 9 seconds before module connects again.Remains low when module is connected.
v) WWAN_LED_N (pin no.106) goes high after module disconnects (LED off), and goes low (LED on) 6 to 9 seconds before module connects again.Remains low (LED on) when module is connected.

What do you think is going wrong?