In certain situations when chunk is unloaded and re-loaded back in scanners placed in manipulators that are connected over wired cable network seem to break and when scan() is called function never returns and just hangs.

I have been unable to create reproduction steps other then it seems to happen to left \3dexport machine in this screenshot (but not to right one which implies some kind of directionality).

Right clicking modem twice to disconnect and re-connect peripheral seems to fix the issue.
I was unable to re-create this issue in singleplayer or in any other location but it happens reliability to this machine.