Well if you can bridge the Arris, you'll need to check with Arris or your ISP service if this can be done. It's preferred to Bridge any modem/router if possible if your going to use an external router. If you can do this to the Arris, then by all means, the DIR-615 is a good router to use as the main host router.
If you think the DAP-1360 is bad, I would recommend that you ask D-Link to RMA it as soon as possible. It will be up to you on when this happens though. I recommend testing the DIR-615 if possible and then after that, if the DAP still does not work well, then you'll know and you can tell even after installing the 615, the DAP still fails and to RMA it. I would recommend testing it on a different PC to be sure that the problem follows, if this is possible, say at a family or friends place.
However If you can't bridge the Arris modem at all, my original suggestion of letting be your main host router, shutting OFF the AP and installing a NEW wired AP at the modem point should resolve this. If your not confident in the DAP-1360, you could install the DIR-615 as a wired AP at the modem point using this:
Bridge Mode vs Relay vs Acess Point (AP) / Routers vs Dedicated Acess Points (AP)Just be aware that the 615 can't perform any bridging operations like the DAP does so it can only work as the wired AP if you choose to go this route.
Yes, a Router is different from a wireless device. We like to keep it differentiated and specific as possible so everyone is clear on what problems are and don't get confused.
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