diff --git a/src/qcodes_loop/data/hdf5_format.py b/src/qcodes_loop/data/hdf5_format.py
index 58be4fd3..814da1d3 100644
--- a/src/qcodes_loop/data/hdf5_format.py
+++ b/src/qcodes_loop/data/hdf5_format.py
@@ -285,7 +285,9 @@ def _create_dataarray_dset(self, array, group):
             name = array.array_id
 
         # Create the hdf5 dataset
-        dset = group.create_dataset(array.array_id, (0, 1), maxshape=(None, 1))
+        dset = group.create_dataset(
+            array.array_id, (0, 1), maxshape=(None, 1), dtype="f4"
+        )
         dset.attrs["label"] = _encode_to_utf8(str(label))
         dset.attrs["name"] = _encode_to_utf8(str(name))
         dset.attrs["unit"] = _encode_to_utf8(str(array.unit or ""))
diff --git a/src/qcodes_loop/measure.py b/src/qcodes_loop/measure.py
index 1c93e808..d9d27cb0 100644
--- a/src/qcodes_loop/measure.py
+++ b/src/qcodes_loop/measure.py
@@ -2,6 +2,7 @@
 from datetime import datetime
 from typing import Optional
 
+import numpy as np
 from qcodes.metadatable import Metadatable
 from qcodes.parameters import Parameter
 from qcodes.utils import full_class
@@ -101,7 +102,9 @@ def run(self, use_threads=False, quiet=False, station=None, **kwargs):
                 # The original return was an array, so take off the extra dim.
                 # (This ensures the outer dim length was 1, otherwise this
                 # will raise a ValueError.)
-                array.ndarray.shape = array.ndarray.shape[1:]
+                array.ndarray = np.reshape(
+                    array.ndarray, array.ndarray.shape[1:], copy=False
+                )
 
                 # TODO: DataArray.shape masks ndarray.shape, and a user *could*
                 # change it, thinking they were reshaping the underlying array,
diff --git a/src/qcodes_loop/plots/qcmatplotlib.py b/src/qcodes_loop/plots/qcmatplotlib.py
index 32c40f5b..dff36c4d 100644
--- a/src/qcodes_loop/plots/qcmatplotlib.py
+++ b/src/qcodes_loop/plots/qcmatplotlib.py
@@ -84,11 +84,21 @@ def __getitem__(self, key):
     def _init_plot(self, subplots=None, figsize=None, num=None):
         import matplotlib.pyplot as plt
 
+        # When reusing an existing figure window (e.g. via clear()), matplotlib
+        # ignores figure-level kwargs such as figsize and emits a warning. In
+        # that case we leave figsize out of the plt.subplots call and apply it
+        # to the figure directly afterwards.
+        reuse_figure = num is not None and plt.fignum_exists(num)
+
         if isinstance(subplots, Mapping):
             if figsize is None:
                 figsize = (6, 4)
             self.fig, self.subplots = plt.subplots(
-                figsize=figsize, num=num, squeeze=False, clear=True, **subplots
+                figsize=None if reuse_figure else figsize,
+                num=num,
+                squeeze=False,
+                clear=True,
+                **subplots,
             )
         else:
             # Format subplots as tuple (nrows, ncols)
@@ -106,9 +116,16 @@ def _init_plot(self, subplots=None, figsize=None, num=None):
                 figsize = self.default_figsize(subplots)
 
             self.fig, self.subplots = plt.subplots(
-                *subplots, num=num, figsize=figsize, squeeze=False, clear=True
+                *subplots,
+                num=num,
+                figsize=None if reuse_figure else figsize,
+                squeeze=False,
+                clear=True,
             )
 
+        if reuse_figure and figsize is not None:
+            self.fig.set_size_inches(figsize)
+
         # squeeze=False ensures that subplots is always a 2D array independent
         # of the number of subplots.
         # However the qcodes api assumes that subplots is always a 1D array
diff --git a/src/qcodes_loop/tests/test_plots.py b/src/qcodes_loop/tests/test_plots.py
index afe2757a..83e86a68 100644
--- a/src/qcodes_loop/tests/test_plots.py
+++ b/src/qcodes_loop/tests/test_plots.py
@@ -37,6 +37,19 @@ def setUp(self):
     def tearDown(self):
         pass
 
+    @classmethod
+    def tearDownClass(cls):
+        # The remote pyqtgraph process spawns daemon threads that forward the
+        # child's stdout/stderr to sys.stdout/stderr. If the process is left
+        # running until interpreter shutdown, those threads can try to write to
+        # a stdout that pytest has already closed, raising
+        # "ValueError: I/O operation on closed file". Shut the process down here,
+        # while stdout is still valid.
+        if not noQtPlot and QtPlot.proc is not None:
+            QtPlot.proc.join()
+            QtPlot.proc = None
+            QtPlot.rpg = None
+
     def test_creation(self):
         """
         Simple test function which created a QtPlot window