Check - congratulations on a very enjoyable (and challenging) puzzle.
I was temporarily side tracked by the appearance in the grid of two groups of 5 contiguous cells which include all the letters of the last word of step 4. I wondered for a while if they needed to be rearranged to fulfil the step.
The chances of these five letters apperaring randomly in contiguous cells only once would appear to be small, but twice seems very unlikely indeed.
Was this a deliberate red herring. If so it makes construction of the puzzle even more impressive.