I presume the ISP gateway/modem isn't equally or more so to blame for internet cutting out? If it is indeed the Asus gear, then it may be time to move on.
If budget is less of a concern and you want arguably the most reliability with the fewest moving parts, go with Cisco small office gear (three pieces of hardware, that's it). For <800Mb of internet, an
RV260P and two
CBW240AC access points. For gigabit internet, an
RV345P instead of the R260P. Unlike UniFi or TP-Link Omada, the wireless controller is embedded (into the AP firmware), so no separate controller instance to setup or rely on, and the PoE switch and gateway are converged into a single box. Cost, though, would be $560-770.
If the Cisco approach is too spendy, then UniFi is an option, but honestly for a discrete controller system, TP-Link Omada gives you equivalent link-layer performance for lower cost (minus the hardware diversity). I would do a TL-R605 router, TL-SG2008P switch, two EAP245's and the OC200 controller, or host the controller for free as a software install on an always-on PC, RPi or server/VM). Total cost will be $350-430, depending on if you buy the OC200 or host the controller yourself.
Either way, you'll have cleaner, higher-capacity wifi and a network that runs more like an appliance and less like a toy.