Running compressible NS, a matrix_bank is created at line 208 in file pyfr/solvers/base/elements.py scal_upts_inb,

```
# pyfr/solvers/base/elements.py scal_upts_inb (line 208)
self.scal_upts_inb = inb = backend.matrix_bank(self._scal_upts)
```

Later, at line 65 in file pyfr/solvers/navstokes/elements.py, this bank gets passed as an arg to self._slice_mat(…)

```
# pyfr/solvers/navstokes/elements.py (line 65)
u = lambda s: self._slice_mat(self.scal_upts_inb, s)
```

If I run this sim from a command line, all is ok. Likewise, when run as a Visual Studio 2019 project, all is ok. But when stepping through with the VS debugger, I get stopped at line 159 in file pyfr/backends/base/types.py,

```
# pyfr/backends/base/types.py (line 158)
if isinstance(mat, MatrixBank) and any('bank' in m.tags for m in mat):
raise TypeError('Nested MatrixBank objects can not be sliced')
```

If I comment out this check, then the sim runs fine under the debugger. Which got me wondering if this restriction on slicing a MatrixBank still applies?

Below is the .ini file I’m using:

```
[backend]
precision = single
rank-allocator = linear
[backend-cuda]
device-id = local-rank
[constants]
gamma = 1.4
Pr = 0.72
mu = 1e-5
uin = 0.2
[solver]
system = navier-stokes
order = 4
anti-alias = none
shock-capturing = artificial-viscosity
[solver-artificial-viscosity]
kappa = 5.0
max-artvisc = 5.0e-5
s0 = 7e-4
[solver-time-integrator]
scheme = rk45
controller = pi
atol = 1.0e-6
rtol = 1.0e-6
min-fact = 0.3
safety-fact = 0.80
max-fact = 1.20
dt = 1.0e-5
dtmin = 1.0e-10
tstart = 0.0
tend = 1.0
[solver-interfaces]
riemann-solver = hllc
ldg-beta = 0.5
ldg-tau = 0.1
[solver-interfaces-line]
flux-pts = gauss-legendre
[solver-elements-quad]
soln-pts = gauss-legendre
[solver-elements-tri]
soln-pts = williams-shunn
[soln-plugin-nancheck]
nsteps = 100
[soln-plugin-dtstats]
flushsteps = 100
file = dtstats.csv
header = true
[soln-plugin-writer]
dt-out = 0.5
basedir = .
basename = ns_{n:03d}
[soln-bcs-inflow]
type = char-riem-inv
rho = 1.0
u = uin
v = 0.0
p = 1.0
[soln-bcs-wall]
type = no-slp-adia-wall
[soln-ics]
rho = 1.0
u = uin
v = 0.0
p = 1.0
```

thanks - Nigel