You created your scaled_inputs_all DataFrame using loc
function, so it most likely contains no consecutive indices.
On the other hand, you created shuffled_indices as a shuffle
from just a range of consecutive numbers.
Remember that scaled_inputs_all[shuffled_indices] gets rows
of scaled_inputs_all which have index values equal to
elements of shuffled_indices.
Maybe you should write:
scaled_inputs_all.iloc[shuffled_indices]
Note that iloc provides integer-location based indexing, regardless of
index values, i.e. just what you need.