I soft locked the elevator to bring down the 3rd explosive.
I believe because I managed to jump around to do the power management room before I had brought the lift down initially, I jumped around between the fence and the small outcrop of the control room windows, it skipped the re-enabling of the controls triggers.
It also locked the small side door to go back through to make sure i didn't miss anything or it hadn't reset after I did do the 2nd section.
I had to use no-clip to go back and found that there was nothing I could do left, and just used no clip again to go onto the elevator platform and push the crate off, after a few tries, to a point i could move it into the canal as normal.