frappy_psi.picontrol: reset overflow to 0 on when changing target

frappy_psi/picontrol.py

@@ -290,7 +290,7 @@ class PI(HasConvergence, PImixin):
         return self.input_module.read_status()
 
     def write_target(self, target):
-        self._overflow = 0
+        self.write_overflow(0)
         super().write_target(target)
         self.convergence_start()