Auto-Sweeper keeps loading Large Solid Oxidizer Tank indefinitely

I had exactly the same issue. Auto-sweeper would deliver gramms of oxydiser indefinitely, even when the oxydiser tank was to full capacity.

Also I've noticed that the "filling port" for solid oxydiser module is in the middle tile and the closest You can place the ladder to manually load oxydiser into it is on the 3rd tile from the middle which makes it impossible to load manually by the dupe.

I did a workaround though: placed narrow module (like small cargo) under the Oxydiser tank, then built a ladder that overlaps with the oxydiser tank, then deconstructed small module. Dupe can now stand on the "invisible" ladder and deliver oxydiser.