You could eliminate the router from the mix. You could run a cable from the computer directly to the modem. Note: you always have to reset the modem whenever you connect a different device to it.
Edit: to add the words c"Just for Testing Purposes".
Understood. Just for test you could bypass the Router to see if the failure abates. If so that would point to a Router issue.
A possible alternative would be, again just for test, run one of the Laptops with an ethernet cable directly to the Router. If that works that would point to a Wireless issue.
Another alternative would be to log in to the Router and change the wireless channel to either 1 or 11 (As far from the current channel as possible)