Long story short,

I have a film strip with images made of what I assume is only or mostly silver iodide (or other non developable silver salts).

It is an E-6 film, the machine borked, and the film sat in the first dev at processing temp (with no agitation) for an hour or so, I was going to rehal it into a colour neg as there was fine negs on the film, but I had already hit the colour dev by that stage and didn't want to stack a neg on a pos.

Anyway, the results are, quite thin black and white positives, which survived the bleach and fix. There is no dye.

This has happened once before, when T-Max was accidentally run through it (inc bleach and fix), it gave the same results, thin black and white positives.

Assuming it's a silver layer that won't budge with any combination of steps of bleach, colour dev etc (and fix), what can I do to get this to a developable silver salt? I can then rehal it over and over to reasonable density slides.

Eg; such as passing the film through chlorine gas to get it to silver chloride?

Would a ferricyanide/bromide bleach do the trick and displace the iodide, that PDTA based bleach doesn't seem to?