3: A 2% solution of sodium sulfite should be perfectly clear, and not show any sign of sediment.

Since yours did, there's something else in it. My first guess is that it's been mixed with "hard" water, so that you've got calcium sulfite (and sulfate) coming out of solution.

If the wash water is also "hard", you'll have a little calcium absorbed in the emulsion which reacts with the sodium sulfite again, leading to even more white stuff! So it's not the HCA which is still in the prints, it's a trace of calcium sulfite/sulfate.

After washing, give the prints a few minutes in deionised water. Use deionised water for mixing "HCA", or filter the solution before use.