Do you use Java 8?
No

What version of Minecraft do you use?
1.12.2

What version of MinecraftForge do you use?
14.23.2.2616

What version of Immersive Engineering do you use?
0.12-76

What version of Immersive Cables do you use?
1.2.0.1

What is the issue / bug you have encountered? Give us a short description.
IC wires on all connections disappear. (All wire types) (only when reloading)
It isn't possible to reconnect, and the relays/transformers must be removed, and replaced before the wires can be reconnected .

How can it be reproduced?
Re-load/load world (full restart or otherwise)

Please post your log file (either in /logs/fml-client-latest.log or /logs/latest.log) on https://gist.github.com and provide the link:
https://gist.github.com/NefariousFox/cfa247351bba589c5fdba6e614467c2d

does the network still work even if they're not visually connected?
Also try out 1.3.0 of the mod (with IE 0.12-78 or newer), there were some changes on the wire API.

(Also you use Java 8, the log says so)

Interesting, I definitely don't remember installing 8...

I'll update both and let you know if I can repeat the same problem. (No, they weren't still operating with the wires missing)

Any updates on this?

I know I'm late to the party, but it was revealed a while ago that ImmersiveTech had copied a bunch of code from Immersive Engineering and was calling certain parts incorrectly, and was causing this issue for all cables in the game. Immersive Engineering added a workaround to prevent other mods from breaking cables as of 0.12-90, so this is likely fixed now.