Ultimate Mega Factory

This is my rocket fuel power plant. There are many like it, but this one is mine.

Help please. How to make a standard 4 way intersection work with signals? I’m placing path signals at each entry, block signals at each exit. But the intersection shows as occupied even though there’s no train there.

This is the last thing I built in my first playthrough. I used a planner for the first time to help design it. It produces 20 Alien Power Matrices per minute.