Brando_Miranda:

This is a very confusing error message


The error message points you towards valid indices for a single dimension, which are -1 and 0:
x = torch.randn(1)
print(x[0])
print(x[-1])
print(x[1]) # error

You are passing a list of scalars to torch.stack, which cannot stack them in dim1.
What shape do you expect in x_proc?