I can confirm this Bug. I Think this happened sometimes after some Game updates. I think the issue is, that the Belt is not Really connected anymore. I tested to fix this Bug, with upgrading the Belt. (This doesnt help). During deconstruct and reconstruction, i noticed that the shape/ length of the Belt was slightly different.
I had this Bug in some factories, where i know, that they have really worked before.
Because this Game is in Early Access and under development, such thing can happen.