Weighted percentage CPU value is updated only if a process is taking non-zero percent of CPU. Issue is reproducible for example with following steps:

1. Play some flash video in firefox browser (so it takes considerable amount of %CPU, let's say 50%).
2. After a while, when %WCPU of firefox grows let's say to 20% close the firefox tab with the video.
3. Value of %CPU should now drop to 0% while the value of %WCPU remains approx. at 20% and does not decrease.

It should be reproducible with any process that takes "lot of CPU" and then drops to 0% CPU.

Tested on qps version 1.10.12.1 compiled for amd64 linux platform.