@Sgt Mandaville I would get onto your ISP and see what they can tell you about it from their side, mostly they'll run through their useless BS such as speed tests and changing to dual-band and such to lighten the load even though in my experience it doesn't do much. Currently I have the same kind of issue and the engineer that comes out to change my router has come out enough to 'fix' issues that we've gotten to know each other and he tells me even with an unlimited plan or any plan, that the ISP will tend to throttle you especially at peak times to adhere to everyone on the line, kind of like trying to balance it out which can sometimes cause the drops. It can happen at weird times as well like late at night or early mornings as well but sometimes he says that may be due to maintenance.
My modem is built into the wall and sometimes the cable between it and the router may also fall loose, it can literally happen at random times or sometimes there can be dust or debris in the socket at the modem which can cause issues as well. I suggest when you have some free time to just scan over the hardware for anything that looks odd.
Apart from that I can't really suggest more, you could try allocating a device to the DMZ, Dual-banding (if your router supports it) and even clearing some useless ports. Hopefully you get it all figured out.