Modem loses internet connection and cable error RDK-03033

For several months now, my modem loses internet connectivity daily. Tech support came out and said it was due to the amplifier settings being too high because the amp was configured for when I had 5 tvs connected and a modem. Once Cox went to digital boxes only (many years ago), I started using only 1 tv and modem but no one ever came out to modify the amplifier. The tech support guy made some changes and the modem worked fine for about a week but then reverted back to cycling connectivity. This time, every time my modem goes out, my cable box becomes unresponsive to the cox remote and an error pops up, RDK-03033. A 2nd tech support guy came out and said it was a splitter issue so he replaced the splitter that splits the signal from the outside cord to my cable box and modem. It didn't resolve the issue. Now, when my modem and cable box go out (multiple times a day), I have to go into the attic unplug the input cord to the splitter and both the modem and cable box immediately start working again. It may last a couple hours, it may last 10 minutes. Any idea what the real issue could be? I am finding it hard to justify spending $225/month for services that aren't functioning properly and I can't seem to get a service technician that knows how to troubleshoot the real issue.