If you EN plate a steel part with steel bolts installed, the EN plating will be continuous over the steel surface. So, of course it will have to fracture when you torque the bolt out.
Just tell the plater which holes to plate and which to mask/plug. Also, where you want the parting line if some are countersunk or have o-ring lands. Also, for heavy parts, let the plater know preferred support points.
SOP for platers.