The siphon toilet drains the bottom dirt and water together through the negative pressure caused by the water flow, rather than through mechanical or electric drive.
If there is still slag return after flushing, it may be because the toilet drain or sewer is blocked or bent, or the water pressure is insufficient.
The solution is to use a professional pipe dredging tool to clean up, or contact a professional maintenance technician to repair the toilet drain.
If it is a water pressure problem, you can adjust the water pressure or use a booster pump to increase the water pressure.
Just rinse it again with a small amount of water