this is how it looks like
https://youtu.be/UcfvHVFG3FA

what happens if I reconnect to the server
notice how one mill is stopped, and after rejoining theiy both rotate
https://youtu.be/70FnK7S4pNM

version 1.16.3
mod version 0.3

i guess this happens because they are connected in a row and thus when i stop one, another one keeps rotating and makes the stopped one continue rotation as well, even though it's not shown on client side as rotation

This was addressed in 0.3c, please re-open if this is still an issue.