Doom 64: The Absolution (weapon problem)

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I’m going through the Steve Searle add-on “The Reckoning” and there is a problem - on map 03 “Delta Quadrant” I can’t get to Unmaker.
I do not see the right button or portal. According to port restrictions, a jump is not possible. Maybe someone has a solution?

Video from the scene: https://youtu.be/tvdxyRExhOc

 

Spoiler