Prime95 Slow workers/freeze

[Born_2_Kill_83]

Im trying to get a stable O/C with my 3770k after its decided what was stable 4 months ago isnt good enough anymore.
Anyway Im stressing with prime95 and while I get no errors or crashes with the settings Im using Ive noticed some "workers" (different everytime) either become very slow or get stuck completely.

What causes this and any fixes?

 

[Born_2_Kill_83]

To be completly sure I tested at stock everything and still the same frozen workers