You don't have a cat in hells chance of getting it swapped for a modem.
It seems to work for me using wired connections with no problems after turning off the SPI (firewall features) and flood detection (find these in Advanced settings/Services). I turned UPnP off too as I don't need it and have found it can cause problems with some routers.
I don't use P2P which is well known for busting iffy routers by blowing their maximum supported connections.
I only use wireless for phone and iPad but even that light usage has caused it problems a couple of times and I've had to reboot it before I could connect.
Firmware that supports bridge mode is promised but no timesscale was given.
If you can't fix it with a hammer you've got an electrical problem.