Comment 2.4GHz - 5GHz (Score 1) 499
I think one of your neighbors is talking to someone at the same time every night using his cordless phone. This could cause the type of interference if you are operating on the same channels and your antennas are positioned such that the RF waves are canceling each other. Try rotating your router 90. Seriously. Or if possible set your router to 5Ghz mode exclusively assuming your neighbor has a 2.4Ghz Phone.