# Overwriting MPS tensors loses/invalidates index information?

I'm working through an algorithm that uses this partial Kronecker product formula for each tensor of an MPS in v3. Matt's solution (see link) works great for individual ITensors. Unfortunately, I can't seem to get this working the same way for the tensors of an MPS. I get an error about "different index structure".

I've tried brute-forcing the tensors to have the exact same indices several different ways with no luck. I suspect that this error has something to do with overwriting the MPS tensors as I compute them; is there a "correct" way to do that? I suppose I basically want to build an MPS from scratch, given that I know what the indices should be and what the tensors should be.