For some reason, I found the Honkai: Star Rail “Signs of Fragmentum,” Difficulty III stage’s Wubbaboo to be the easiest ones to find. Like the second stage, there are five hidden around. The only real trial here is that some of the monsters are rather difficult, due to this being a recommended level 38 map. So even though you can’t access the overall map, the light panel puzzles and hidden Wubbaboo locations are pretty obvious.
The first Wubbaboo is right in the elevator shaft you step out of when the challenge begins. Just run around and look down. You should see the little buddy floating like in the screenshot below.
The next two Wubbaboo are near the strong enemy across the bridge. One is hiding under the bridge, while the other is just past the light panel puzzle. However, because of the positioning, you can only get the one floating near the bridge after you finish that puzzle. Here’s that light panel solution:
Scan that Wubbaboo, then turn around to scan the one floating near the bridge to get these two in Honkai: Star Rail “Signs of Fragmentum,” Difficulty III.
To get the next Wubbaboo and reach more enemies, you need to complete another light bridge. Again, this is a simple one.
Right after you pass over the bridge and enter the room, look to your right. The Wubbaboo is right there.
Finally, walk out of that room. Head to the series of rooms at the other end of this extension. The last Wubbaboo in Honkai: Star Rail “Signs of Fragmentum,” Difficulty III is at the end of the dead-end hallway in the series of rooms ahead of you. After you defeat the enemy, you’ll see it floating above the window.
As a reward for meeting all objectives, you can get a three-star Guard’s Shining Gauntlets Relic, a three-star Guard’s Silver Greaves Relic, 5 Adventure Logs, 5 Condensed Aethers, 60 Stellar Jades, and 10,000 Credits.
Honkai: Star Rail is available for PCs and mobile devices, and PS4 and PS5 versions are in development.