Grave Concerns - Waterdeep Faction Adventure

I like the premise of this adventure, but it has numerous flaws that makes it unplayable in my opinion.
The shaft is 15x15 ft wide and players are pulled downwards at 10ft per turn, and the ledges the players must reach are 2ft deep. What this effectively means is that any creature without a flying speed (or ability to glide through the air like the Hadozee) is doomed to fall all the way to the bottom of the shaft and end up in Undermountain, unless they use a grappling hook or the like to grab hold of a ledge. Furhtermore, the dimglobe only emits light in a 10ft radius, meaning it's very possible to not see the various ledges unless the character holding the globe is falling in the exact center of the 15ft wide shaft. As fascinating this dungeon is in a fantasy sense, it is impossible to solve for anyone but the most well-prepared adventurers.

Another issue is the 1st (intended) section of the dungeon. A riddle tells the party to light "up and down then again" (referring to areas...See more 1d and 1e). But this order doesn't make sense if you look at the map of the dungeon. While area 1d is undeniably above area 1e, it is only reachable via area 1h, which is far below area 1e from the player's view. The spatial anomaly also doesn't make it less confusing for the players. What makes it worse is, again, the shaft. A player can certainly drop from area 1a down to 1h and continue up to 1e, but then the'd be stuck. There is no way (bar flying speed or climbing speed) for a player to make it up to area 1a (and later 1d) again. So the riddle should be "down and up then again".

But that's not the worst part about the riddle. To solve it, the lights must be lit within *one round* of each other using the (one and only) dimglobe. I've calculated the movement speed a character requires to do this (without any form of teleportation): 55ft from 1d to the shaft, 100ft flying (including compensating for the 10ft magical downwards pull), then 60ft from the shaft to 1e, 60ft back, 90ft flying speed (to forcefully fly downwards), 55ft back to 1d, 55ft back to the shaft, 90ft flying speed upwards, and 60ft back to 1e.
All in all: 345ft movement speed and 280ft flying speed. When a party manages to do all this, they get to fight 2 wraith warriors who, when defeated, drop a cursed +1 sword.

I like the concept of this adventure, but it seems like you didn't think it through and playtest it. I would suggest a redesign of the dungeon, one in which the gravity thing can be counteracted by the players via some magical item like the dimglobe. I would also suggest adding more space for a fight against Losser to take place in.