Paradox Junction has a nasty habit of making you feel safe for about five seconds, then punishing you for it. If you're trying to push rounds, you'll want the Sundergat sooner rather than later, and practicing setups in a CoD BO7 Bot Lobby can help you get the muscle memory down without wasting a full run. The big thing to remember is this: the Sundergat isn't a lucky box pull. It's an upgrade path, and it starts with building the Blundergat properly, every time.
Your whole route revolves around the Cul-de-Sac workbench, the one with the grimy vise bolted to it. Grab the four build parts around the map, bring them back, and craft the Blundergat there. Sounds basic, but people still mess it up by wandering off and treating the bench like a "one-and-done" stop. Don't. You'll be coming back here for the kills, for the Mimic, and for the timeline step later. Also, don't blow your salvage on random toys right away. You want ammo and breathing room, because the next part is less "solve a quest" and more "control the chaos."
After a round wraps, watch and listen for the blue-flame tornado zombies. You'll hear the crackle before you see them, and the vortex effect gives them away even in a messy train. The mistake is panicking and deleting them from across the street. Instead, clear the regular zombies first, then keep that special one alive and walk it over to the workbench like you're escorting a toddler through traffic. You need to kill two of these, in order, right next to the bench with the Blundergat. "Close" really means close—if you're a few steps off, it just won't count and you'll hate yourself for it. Once the second one drops correctly, a Tortured Mimic spawns. It's chunky, it hits hard, and it loves catching you mid-reload, so keep a stun or a safe loop ready, but make sure it dies by the bench as well.
Now for the part that trips squads up: the map's split between the clean "past" and the wrecked "present." You need the past version. Wait for the flip, or burn essence on a cracked golden portal if you're trying to stay on pace. Find the workbench in the past, give it a melee smack to "wake" it, then place your Blundergat on it. After that, swap back to the present-day ruins and let the transform animation play out—this is where the Sundergat shows up. Keep your head on a swivel during the swap, because Rad-Hounds love to wander in and ruin the moment with an explosion you didn't even see coming.
The smoothest runs are the quiet ones: one player kites, one player clears, nobody gets cute with a sniper shot at the wrong target. Call out the blue-flame spawns, and tell your team you're "walking it to bench" so nobody accidentally steals the kill. If you're solo, just slow down—thin the herd first, then do the escort. And if you're trying to dial in the timings or learn spawn rhythm without the stress, cheap CoD BO7 Bot Lobbies are a decent way to rehearse the sequence and stop throwing runs to one bad bench kill.