Yes, your changes break vectorization - as I said it is very brittle. If you view godbolt. org, my code has characteristic AVX instructions (suffix ‘ps’ for packed single) and “add     rsi, 32” line that is a step over 8 floats. Big chunk of code below handles 0-7 tail elements.
More practical way is enabling compiler diagnostics, that may say the reason why auto-vectorization failed (the message may be obscure though).