Description

I am working with an UnstructuredGrid and I want to plot the quantity over a line. The quantity (called 'eps') is defined at the nodes of the grid.
I saved the .vtk file for my grid (see below). Plotting the quantity gives me the result I expect. The same is true using slices. These two methods both give me a value that is non-zero everywhere.
However, if I produce a linecut of the same quantity 'eps' using the sample_over_line method, then some spurious zeros appear in the output data. This can also be seen using plot_over_line.
This appears to be a bug, since my quantity should not be zero along this linecut. This can easily be seen from the 3D plots.
I am using pyvista version 0.25.3 along with vtk version 9.0.1. I had the same issue with pyvista 0.24.2. I would appreciate to know what could be causing this.
Here is the code that shows the apparent bug.

""" sample_over_line.py: Test pyvista function sample_over_line."""

__author__ = "Felix Beaudoin"
__copyright__ = "Copyright 2020, Nanoacademic Technologies Inc."

import pyvista as pv

# Load vtk file and initialize grid
path = "pyvistagrid.vtk"
grid = pv.UnstructuredGrid(path)

# Plot the quantity 'eps' stored in .vtk file
# It is clearly non-zero everywhere
# This is also true when inspecting the .vtk file
grid.plot()
slices = grid.slice_orthogonal()
slices.plot()

# Now plot over a line from x=-12e-9 to x=12e-9 at z=5e-9 and y=0.
begin = [-12e-9,0,5e-9]
end = [12e-9,0,5e-9]
grid.plot_over_line(begin,end,resolution=100)

# The plot shows dips at which 'eps' goes to 0 exactly
# This is also seen by directly printing the linecut
linecut = grid.sample_over_line(begin,end,resolution=100)
print(linecut.point_arrays['eps'])

Example Data

The vtk file used in the code is also attached in the following zip file.
pyvistagrid.zip