Thats no bug, its just different from before.
Look at the old transparency screenshots. You maybe see that the wires make the frame transparent( Its a very small screenshot so I am not shure). This was the bug that made usage of transparency nearly impossible. What we sadly lost is semitransparency using transparency in textures, but it was a good deal in my opinion compared to the unusable state before! Its basically the same way as it was made with the tileset objects before.
What you maybe have to do now is to make semitransparent things a bit more less transparent. In your case the wires musst be less transparent.
In other words the contras between transparent and not must be more sharp!
Try it, I bet you will be happy with the result.
