FYI for the Peplink community. Over 2 years after the first reports of problems linking Peplink routers to assorted cable modems, I experienced this, yet again. The router was a 2nd generation Surf SOHO, the cable modem a Netgear CM600.
Router was running fw 7.1.2 and upgraded to 8.0.1. After the mandatory reboot, it could not find the modem. Rebooting the router back to 7.1.2 did not help. Rebooting modem did not help. Had to power off both devices, boot the router, then boot the modem. Lots of anxious moments.
The support.cgi page showed Ethernet frames being transmitted and received without error. I collected pcaps using the support.cgi page, but this is after the problem (I would think) and I am an amateur at using Wireshark. I opened a problem ticket, but it shifted blame, suggested adding a switch between the two devices and ultimately went nowhere.
Prior Forum postings show this was fixed for 3rd generation Surf SOHOs. Not sure about the Balance line. Again, just an FYI.