Auto-sweeper delivers Regolith to Sieve in endless fail loop

That's weird, I loaded the save and the filtration medium got delivered normally after a while.

Could it be you were seeing the sweeper fail while there was still some filtration medium in the sieve, and the sweeper was failing because the sieve was getting periodically blocked by the slow outflow rate?

 

The sweeper will succeed once the regolith in the sieve runs out completely, at which point the pipe can no longer get blocked. 

I had a similar issue with oil wells and their input pipe, and that got fixed: 

Until then, you can automate the sieves with those liquid reservoirs so they stay off if the pipes are full.