shuttering pads

[jigger80]

iv just done a total rebuild on the front brakes,new seals,braided lines new hh pads,the works!!anyway at slow speeds the pads seem to shutter,it first came to light today in the rain for the first time,could it be the cause of the temperature dropping due to not really touching the front in the wet??
in the dry i never got it,everything is in place and free moving,also the anti-rattle plates are in place,any ideas anyone??