After I enabled asteroid regeneration on my lan server I noticed that server ticks take 2-10 seconds. From logs I understood that some astersoids generated too close to each other and got stuck. After several minutes lags had gone away. But after mining ot a few more asteroids, these lags happened again (several times as I mined more of them).
Another few hours later I found groups of 2 to 3 identical asteroids very close to each other. Now asteroid regeneration is turned off, but I made copy of the whole world when I found these duplicates.
I wasn't able to reproduce it on fresh test server.