Super slow speeds at night

My speeds drop down to a crawl at night during peak hours. Have been doing it for months now. Called cox, they said it’s my modem, bought a new one, same issue, they came out, said the tap was rusted, replaced it, same issue. I’m thinking it’s a network problem on their end and I’m extremely frustrated. I’m dealing with speeds as slow as just a couple Mbps most nights. Wondering if anyone else in the North Las Vegas area is experiencing this.