Every chock creates magnetic field. The pulse frequency reflects to the ground plane causing current disturbances. The easy way is to remove any copper plane underneth the chocke. Here is an example how NOT to route the copper plane underneth the chockes:
Red is the top layer, green is the next inner layer. L8 (3V3) and L10 (15V) are the chocks on the output line. The signals on the both chocks are shown below:
The pulse frequencies direct influence the copperplane and further disturbes the signals and their function.