An acidified solution of thiosulfate is unstable and will eventually throw down a precipitate of sulfur. This reaction is called sulfurization. To slow this process down sodium sulfite is added to the mix. It will combine with the sulfur and produce thiosulfate ion.

SO3-2 + S --> S2O3-2

While it appears that you have resurrected the fixer for now remember all the sulfur on the sides of the container. Fixer is cheap but film and paper is expensive so this is really a false economy. The chemical balance of the fixer has been compromised. I would toss it.