You can't adjust qam levels at a converter or modem, make sure what your levels are coming out of the tap, if bad there call a line tech. If they are good there it's your baby from the tap to the TV. Drop, connectors, etc can suck out individual qams.
Life is what happens while you're busy making other plans
This is CABL.com posting #337372. Tiny Link: cabl.co/mbzVE