diff --git a/gprMax/cmds_multiuse.py b/gprMax/cmds_multiuse.py
index 9fb768cc..c6dfa146 100644
--- a/gprMax/cmds_multiuse.py
+++ b/gprMax/cmds_multiuse.py
@@ -390,7 +390,7 @@ class HertzianDipole(UserObjectMulti):
 
 
         # Check if there is a waveformID in the waveforms list
-        if not any(x.ID == waveform_id for x in grid.waveforms):
+        if all(x.ID == waveform_id for x in grid.waveforms):
             logger.exception(f'{self.params_str()} there is no waveform ' + 
                              f'with the identifier {waveform_id}.')
             raise ValueError
@@ -526,7 +526,7 @@ class MagneticDipole(UserObjectMulti):
 
 
         # Check if there is a waveformID in the waveforms list
-        if not any(x.ID == waveform_id for x in grid.waveforms):
+        if all(x.ID == waveform_id for x in grid.waveforms):
             logger.exception(f'{self.params_str()} there is no waveform ' + 
                              f'with the identifier {waveform_id}.')
             raise ValueError
diff --git a/gprMax/config.py b/gprMax/config.py
index 162b06c8..cd2025fc 100644
--- a/gprMax/config.py
+++ b/gprMax/config.py
@@ -72,7 +72,7 @@ class ModelConfig:
         #     N.B. This will happen if the requested snapshots are too large to 
         #           fit on the memory of the GPU. If True this will slow 
         #           performance significantly.
-        if sim_config.general['solver'] == 'cuda' or sim_config.general['solver'] == 'opencl':
+        if sim_config.general['solver'] in ['cuda', 'opencl']:
             if sim_config.general['solver'] == 'cuda':
                 devs = sim_config.args.gpu
             elif sim_config.general['solver'] == 'opencl':
diff --git a/gprMax/contexts.py b/gprMax/contexts.py
index fbde3698..bc3004f8 100644
--- a/gprMax/contexts.py
+++ b/gprMax/contexts.py
@@ -53,7 +53,6 @@ class Context:
             results: dict that can contain useful results/data from simulation.
         """
 
-        results = {}
         self.tsimstart = timer()
         self.print_logo_copyright()
         print_host_info(config.sim_config.hostinfo)
@@ -88,7 +87,7 @@ class Context:
         self.tsimend = timer()
         self.print_sim_time_taken()
 
-        return results
+        return {}
 
     def print_logo_copyright(self):
         """Prints gprMax logo, version, and copyright/licencing information."""
diff --git a/gprMax/gprMax.py b/gprMax/gprMax.py
index 91776ca8..6454becf 100644
--- a/gprMax/gprMax.py
+++ b/gprMax/gprMax.py
@@ -214,10 +214,9 @@ def run_main(args):
     # MPI running with (OpenMP/CUDA/OpenCL)
     if config.sim_config.args.mpi:
         context = MPIContext()
-        results = context.run()
     # Standard running (OpenMP/CUDA/OpenCL)
     else:
         context = Context()
-        results = context.run()
 
+    results = context.run()
     return results
\ No newline at end of file
diff --git a/gprMax/grid.py b/gprMax/grid.py
index a4960727..b118019e 100644
--- a/gprMax/grid.py
+++ b/gprMax/grid.py
@@ -414,7 +414,7 @@ def dispersion_analysis(G):
     # Find maximum significant frequency
     if G.waveforms:
         for waveform in G.waveforms:
-            if waveform.type == 'sine' or waveform.type == 'contsine':
+            if waveform.type in ['sine', 'contsine']:
                 results['maxfreq'].append(4 * waveform.freq)
 
             elif waveform.type == 'impulse':
diff --git a/gprMax/hash_cmds_file.py b/gprMax/hash_cmds_file.py
index 845b21d5..fc99385f 100644
--- a/gprMax/hash_cmds_file.py
+++ b/gprMax/hash_cmds_file.py
@@ -278,12 +278,11 @@ def check_cmd_names(processedlines, checkessential=True):
 
         lindex += 1
 
-    if checkessential:
-        if (countessentialcmds < len(essentialcmds)):
-            logger.exception('Your input file is missing essential commands ' +
-                             'required to run a model. Essential commands are: ' + 
-                             ', '.join(essentialcmds))
-            raise SyntaxError
+    if checkessential and countessentialcmds < len(essentialcmds):
+        logger.exception('Your input file is missing essential commands ' +
+                         'required to run a model. Essential commands are: ' + 
+                         ', '.join(essentialcmds))
+        raise SyntaxError
 
     return singlecmds, multiplecmds, geometry
 
diff --git a/gprMax/updates.py b/gprMax/updates.py
index 8c05f560..5f258852 100644
--- a/gprMax/updates.py
+++ b/gprMax/updates.py
@@ -1056,7 +1056,6 @@ class OpenCLUpdates:
                                              self.grid.Hx_dev,
                                              self.grid.Hy_dev,
                                              self.grid.Hz_dev)
-            event.wait()
 
         # If there are any dispersive materials do 1st part of dispersive update
         # (it is split into two parts as it requires present and updated electric field values).
@@ -1076,7 +1075,8 @@ class OpenCLUpdates:
                         self.grid.Hx_dev,
                         self.grid.Hy_dev,
                         self.grid.Hz_dev)
-            event.wait()
+
+        event.wait()
 
     def update_electric_pml(self):
         """Updates electric field components with the PML correction."""
@@ -1158,7 +1158,6 @@ class OpenCLUpdates:
         # if iteration == self.grid.iterations - 1:
         #     return self.drv.mem_get_info()[1] - self.drv.mem_get_info()[0]
         logger.debug('Look at memory estimate for pyopencl')
-        pass
 
     def calculate_solve_time(self):
         """Calculates solving time for model."""