size() returns a vector with at least two elements. Historically, the colon operator ignored everything except the first element of its inputs, but as of R2025a (I think it was) the colon operator starts erroring when given non-scalar inputs.
The code needs to be changed to
for i = 1:size(relarray,1)
for compatibility with previous use.
It would not surprise me if relarray could end up being a row vector though, so potentially length(relarray) might be better than size(relarray,1), perhaps.
