diff --git a/idstools/compute/core_sources.py b/idstools/compute/core_sources.py
index 534900c6..cd194652 100644
--- a/idstools/compute/core_sources.py
+++ b/idstools/compute/core_sources.py
@@ -370,7 +370,6 @@ def get_single_and_total_electrons_ions_waveforms(self, time_slice):
         single_power_waveform = {}
         single_particles_waveform = {}
         dict_single_and_total_electrons_waveforms = self.get_single_and_total_electrons_waveforms(time_slice)
-        total_electron_power_waveform = dict_single_and_total_electrons_waveforms["total_electron_power_waveform"]
         total_electron_particles_waveform = dict_single_and_total_electrons_waveforms[
             "total_electron_particles_waveform"
         ]
@@ -399,7 +398,7 @@ def get_single_and_total_electrons_ions_waveforms(self, time_slice):
                         total_ion_power = 0.0
 
                     total_power_waveform[time_index] = (
-                        total_electron_power_waveform[time_index] + electrons_power + total_ion_power
+                        total_power_waveform[time_index] + electrons_power + total_ion_power
                     )
                     total_particles_waveform[time_index] = (
                         total_electron_particles_waveform[time_index] + electrons_particles
diff --git a/idstools/scripts/bin/plotcoresources b/idstools/scripts/bin/plotcoresources
index c8f7a4b2..a4f9bbd0 100644
--- a/idstools/scripts/bin/plotcoresources
+++ b/idstools/scripts/bin/plotcoresources
@@ -5,6 +5,8 @@ import argparse
 import logging
 import os
 
+import matplotlib
+
 try:
     import imaspy as imas
 except ImportError:
@@ -72,9 +74,11 @@ if __name__ == "__main__":
     time_slice, time_value = get_nearest_time(time_array, args.time)
     ntime = len(time_array)
     nsources = len(core_sources.source)
+    logger.info(f"ntime={ntime}, nsources={nsources}, backend={matplotlib.get_backend()}")
 
     core_source_view = CoreSourcesView(core_sources)
 
+    logger.info("Creating plot canvas")
     canvas = PlotCanvas(2, 4)
     canvas.update_style(args.rc)
     ret = ax_power_profiles = canvas.add_axes(title=r"Power Profiles [MW/M3]", row=0, col=0)
diff --git a/idstools/view/common.py b/idstools/view/common.py
index e8ba5c3c..6b1fd801 100644
--- a/idstools/view/common.py
+++ b/idstools/view/common.py
@@ -21,25 +21,26 @@ def _is_jupyter() -> bool:
         return False
 
 
-# Select the appropriate matplotlib backend
-if _is_jupyter():
-    if "matplotlib.pyplot" not in sys.modules:
+# Select the appropriate matplotlib backend.
+# Honour an explicit MPLBACKEND env var set by CI/scripts — never override it.
+if not os.environ.get("MPLBACKEND") and "matplotlib.pyplot" not in sys.modules:
+    if _is_jupyter():
         try:
             import ipympl  # noqa: F401 - imported to check availability
 
             matplotlib.use("widget")
         except ImportError:
             matplotlib.use("agg")
-elif sys.platform.startswith("win") or "DISPLAY" in os.environ:
-
-    try:
-        import tkinter  # noqa: F401 - imported to check availability
+    elif sys.platform.startswith("win") or "DISPLAY" in os.environ:
+        try:
+            import tkinter  # noqa: F401 - imported to check availability
 
-        matplotlib.use("TkAgg")
-    except (ImportError, ModuleNotFoundError):
+            matplotlib.use("TkAgg")
+        except Exception:
+            # ImportError, ModuleNotFoundError, TclError, or SIGILL-prone libs
+            matplotlib.use("agg")
+    else:
         matplotlib.use("agg")
-else:
-    matplotlib.use("agg")
 
 import matplotlib.pyplot as plt  # noqa: E402