Been a known issue that sometimes occurred, e.g. xJon/Tekkit-2#233:

Every single one of my glass fibre cable blocks disconnect from each other when i go away from my base area to explore the world. I need to exit the server and load back to the server for the cables to return to normal.

An attempt to resolve it would be welcome, thanks :)

@xJon this should be fixed now.
Went through portals (best test case) a ton of times with the patch and it never happened. So thats a good indicator.
(Note that this is the 1.19.2 way so if that doesn't work i have 0 ways to fix it after this)

1.5.9 seems to have fixed this desync issue as well: xJon/Tekkit-2#248

@xJon thank god. Otherwise i would have had no solution anymore.