Ifeel for you. Luckely I didn't have the same experience. These problems have been reported with prints where someSistan residue was left on the print. The proper procedure apparently is:
1. soak in Sistan for the recommended ime
2. wipe off all Sistan residue with a rubber squeegee
3.do not was again; just let it dry.
following this procedure, it seems likely that some Sistan residue is left on the print causing damage. I always used a squeegee, sufficiently large to wipe the entire print clean and thereby never had an issue. I once did a test on the effectiveness of Sistan and decided that a brief direct sulphide toning was sufficient and the better option. So, I dropped Sistan from my workflow.
Interested to hear your direct sulphide process Ralph such as type, dilutions, times and colour change if any?