I have already emailed their support. They are also aware of this issue on some of the routers which maintains timeout after TCP session is closed.
I am thinking about some tweaks that may help. Currently it seems that the app is held after 16300 requests meaning assignment of 16300 ports by the router. Generally, there are 64K possible ports. Are there ports that allocated for wireless / guest zone networks? If I turn off those networks, will I get more ports?