kernel task using cpu 700%

Hi there,

Ch animator went really slow, playing 30 frames animations down to 1.5 frames, and researching the problem I came a cross with this kernel task that uses up to 700% of the CPU  (shown in the activity monitor). Normally stays around 19%. I tried different solutions (turning off behaviours and things alike) and nothing worked. I use an early 2015 15" retina macbook pro plugged to an Apple Cinema Display (thunderbolt). The funny thing is when I disconnected the display to use only the laptop, the kernel task went to normal. Has any one come across this issue? Is it Ch animator or I should contact Apple? Apparently dropbox (I have it in an external drive) also makes the kernel task go crazy.

Cheers to all,

Carlos