High Jitter - and Possible Solution

I recently had call quality issues and ran the VoIP Speed Tester to find out what the problem was. The problem was high jitter at about 80 milliseconds. I did a 30-second power cycle on my routers and the problem stopped. A networking friend told me that sometimes with some routers the router doesn't flush out some variables and over time the quality degrades and power cycling can fix the problem.