diff --git a/src/cal_tools/agipdlib.py b/src/cal_tools/agipdlib.py
index 86e42b1453aba459d67f2ae2d6f2fef80f6b1e18..ea077b5a409691ca41a86c736a75d7b2811d1b6f 100644
--- a/src/cal_tools/agipdlib.py
+++ b/src/cal_tools/agipdlib.py
@@ -202,11 +202,14 @@ class AgipdCtrl:
                 "highVoltage.actual.value")
             default_voltage = None
 
-
         if (
             voltage_src[0] in self.run_dc.all_sources and
             voltage_src[1] in self.run_dc.keys_for_source(voltage_src[0])
         ):
+            # Use RUN source for reading the bias voltage value.
+            # As HED_DET_AGIPD500K2G has a hardware issue that leads
+            # to storing arbitrary voltage values in the CONTROL source
+            # array. e.g. /gpfs/exfel/exp/HED/202230/p900248/raw
             return int(self.run_dc.get_run_value(*voltage_src))
         else:
             # TODO: Validate if removing this and