disappearance of production facilities

It is game year 384; the paper mill is producing concrete slabs, but the paper and concrete slab factories have disappeared from the assembler menu. The existing concrete slab factories are working normally, but it is impossible to continue the game since paper is required for further progress. I tried restarting, but that didn't help. Has anyone else encountered this bug? Is there a fix?

Can you share the save? are you using mods?

no mods

I need to correct myself slightly.
The concrete slab factory hasn't disappeared from the assembly menu; I simply missed seeing it listed separately in the construction menu. However, the paper mill has disappeared from the menu. For the one I already built, the product icon has changed: I'm producing paper, but the output from the factory displays the concrete slab icon—though the factories that use paper to manufacture goods are still operating.
In the meantime, I’ve started a new game and there’s an icon issue: I’m not producing bread yet, only wheat, yet the food market shows the bread icon but not the wheat icon.

I loaded your save and didn't find any issue, can you attach an image of the issue you are seeing?
Paper mill doesn't existing in the game, the chemical plant is the building that produces paper.

Thanks for the help. I'm new to the game and must have messed things up a bit. Thanks for your time.