A third-party network-attached storage device (NAS) or router is unsuitable for use with Time Machine, especially if it's your only backup. I know this isn't what you want to hear. I know that Time Machine accepts the device as a backup destination. I know that the manufacturer says the device will work with Time Machine, and I also know that it usually seems to work. Except when you try to restore, and find that you can't.
Apple has published a specification for network devices that work with Time Machine. No third-party vendor, as far as I know, meets that specification. They all use the incomplete, obsolete Netatalk implementation of Apple Filing Protocol.
Apple does not endorse any third-party network device for use with Time Machine. See this support article.
If you want network backup, use as the destination either an Apple Time Capsule or an external storage device connected to another Mac or to an 802.11ac AirPort base station. Only the 802.11ac base stations support Time Machine, not any older model.
Otherwise, don't use Time Machine at all. There are other ways to back up, though none of them is anywhere near as efficient or as well integrated with OS X. I don't have a specific recommendation.
If you're determined to keep using the device with Time Machine, your only recourse for any problems that result is to the manufacturer (which will blame Apple, or you, or anyone but itself.)
