A single channel with those issues isn't going to cause the problems you are stating. It may slow things down a bit, if you are on 1gb or 2gb speeds, but if you have 250mb speed or slower, which I would assume you have since you only have a 16 channel modem, remember, each channel can handle at least 30mb of data throughput, so 15 channels could theoretically handle 450 mb of data, and your speed is going to be 250 or less.
If you have internet FASTER than 250mb, then you either need to replace your modem with one acceptable for the speed you are signed up for or you didn't post all the signal level information on your modem.
So... What kind of modem do you have, and what speed are you signed up for?