Are the modems that drop out in the same node or nodes? If so check your return path ingress. Also the return level of the modems at the headend. you may have a single problem or a combination of problems. Contact me off the bar and I may be able to help. I have several technicians who specialize in return path problems we may be able to help you out.
My web Page
http://cablejobs.netfirms.com
This is CABL.com posting #102956. Tiny Link: cabl.co/mAWK