Drop down to the lower level to continue on with Jazz's exploration of the Cybertronian ruins. Smash up the two crates at the bottom of the drop to get some money, and then head out into the large, open hall, following the orange arrow posted on the left wall. A staircase will form at your feet, allowing you to get up to the next level and the door ahead. Proceed through the door and use the Teletraan 1 shop embedded in the center of the back wall, behind the device in the middle of the lab. If you haven't started upgrading weapons yet, you will really want to do so now. The upgrades carry over no matter which character you are playing as.
In the next room, loot the goodies from both the left and the right sides of the room beforee pulling down the cetnral door with a grappling hook swing. An enemy will await you on the far wall as soon as you enter. Defeat him and grapple over to the catwalk on the right. Using the crates for cover, pop out and sniper the Decepticons cowering behind cover at the very far end of the hall. From here, proceed safely out onto the main walkway and turn to your right to find rocket enemies trying to get a bead on you. If you are quick with your sniper rifle, you can pick them off before they get off any solid shots. A few regular enemies will be blending in with the rocket troopers over there; don't let them distract you from the real problem at hand, of which we of course mean the rocket guys. Take out the heavies first and then pick off the remaining Decepcitons from a distance one by one. If you need to refill on health, note that there are Energon Cubes behind you on the catwalks and underneath the perch where the enemies fire upon you from. More weapons lie in the Armory Reactors to your right, and more ammo can be found by the Energon Cubes on the platform where the enemies are.
When the room is cleared, head past where the Decepticons were stationed and into the very back right corner, and a little to the left.. You will find a door here. Pull it down with your grappling hook to find a secret room with tons of cash and weapons. Grab what you need and proceed towards your waypoint using your grappling hook to navigate from one point to another. Visit the store along the way if you need to restock on anything (note that the next battle will be a very close range one, and thus your sniper rifle may not be the best choice of engagement anymore,) and then proceed ahead. You will emerge on a walkway that overlooks the Decepticons and their Marauder anti-air units. Open up the door at the end of the hall and proceed down the long hallway and around the corner. As you walk over a vent opening, it will crumble beneath you and send you falling right into an arena. Here you will have to deal with numerous shotgun troops, so as mentioned before your sniper rifle will not be ideal.
The first two enemies will rush you from the opening on the opposite side of the arena from you. You will have plenty of time to prepare for them, as they will have to cut their way through the wall with a torch. If you are unfortunate enough to still have that sniper rifle during this checkpoint, line up the enemies in your crosshairs as they cut through the wall. As soon as you see that reticule turn red (you probably won't even be able to see the actual enemies at this point from all of the smoke and debris flying around) pull the trigger for an instant kill, and then target the second foe as he hits the ground and rushes to cover behind the left hand pillar below. If you don't have a sniper rifle equipped, these initial two enemies might be a bit harder to deal with but the rest of the battle will be much easier. You will want to take up a position to either side of the battlefield where the Decepticons are carving through the wall. Use your grappling hook to soar over to either the left or the right overwatch, and when the Decepticons hit the ground surprise them by mowing them down from the side. You can even use the two explosive barrels stationed by the pillars to take them out faster.
A second wave of enemies will waste no time in coming into the room. You may just hear them coming before you see them, though, and this can be highly dangerous because most of them are Shotgun troopers. They will rush in from the vents in the left and right walls and charge you with everything they have. If you have a powerful secondary weapon like a rocket launcher, now would be a good time to put it to use. Just be sure that the enemy troops don't get so close to you that you suffer or die from the splash damage. More secondary ammo is scattered about the upper corners of the room.
Whatever strategy you decide to put to use against these guys, absolutely do not get up close to them. These guys can use their Scatter Blaster Shotguns to, well, scatter you in about a second, taking you from full health to nothing in the blink of an eye. If you don't come into this battle properly equipped, it can be incredibly annoying. Compounding that annoyance is the fact that you will have to sit through the cutscene of Jazz tumbling through the ventilation grate every time you restart the checkpoint. If you simply cannot manage to get past this checkpoint, whether it's because the weapons you have just aren't cut out for the job, or because the Shotgunners are proving too much for you, we have a little trick you can use to skip past the brunt of the encounter. It's not guaranteed to work, since it is somewhat of a glitch and always succeptable to being patched out at some point. But if you quit the game, turn off your console, turn it back on and reboot back to this checkpoint, we found that not only do you skip past the annoying little cutscene of Jazz falling through the grating, but you also skip past the second and third waves of enemies who will rush in after you deal with the first wave, meaning that you won't have to fight nearly as many enemies.
However you get through the battle, jump down to the lower level and pull the switch in the middle of the room when you are ready to proceed.