Bug with replacing signals

[zook2]

Maybe difficult to find this one, but I recently began to replace old signals on the BB server (West Zodiac Shipping) with ECTS beacons. I built new signaling centres and dragged the new signal along the line, which automatically deletes any older signals. 
It went well at first but today I noticed that my new centres' capacity filled up quickly without me having placed a lot of new signals. Then I noticed that those beacons were showing up in places where I never went to work, seemingly at random among the old ones. I can't currently nail it down any better.