After running for some time (~2 days, hibernation may be at play here), widgets start to draw updates irregularly.
Digital clock: most of the time, every 2 seconds (only other updates coming from net/cpu/mem monitors), sometimes every 1 second, very rarely 3 seconds.
Task switcher: any updates happen only on 1 second boundaries, leading to significant lag when selecting active window.

Reproducible: Sometimes

Steps to Reproduce:
1. Start KDE with the setup described in Additional Information
2. Use for a few days, hibernating between sessions.

Actual Results:  
Digital clock: most of the time, every 2 seconds (only other updates coming from net/cpu/mem monitors), sometimes every 1 second, very rarely 3 seconds.
Task switcher: any updates happen only on 1 second boundaries, leading to significant lag when switching workspaces or selecting active window. (The 1-second boundary aligns with a clock bump, clock bump can be forced by switching windows.)

Expected Results:  
Digital clock bumps the number by 1 approximately every second when not CPU starved
Task switcher never waits for a one-second boundary to update active window highlight.

System uses Intel HD4000 GPU, default Fedora 22 setup.
When panel semi-transparent, underlying windows' updates imediately seen "through" the panel yet the problem persists.
Panel setup: One of 2 panels; vertical. Widgets: CPU, mem, net monitor, task manager, digital clock.