Since patches 1.2.0.0 and 1.2.0.1 also did not resolve this issue, it will likely never be fixed. However, I managed to find a janky workaround using a trainer - of course I won't link anything, since that is pretty gray-zoney, but google is your friend. This likely only works, if you have a save before picking up the rift modulator! Go and pick up the modulator - now turn around and check, if the elevator doors are open, with the elevator itself missing. This didn't always happen for me and sometimes the doors just spawned in after climbing to the 2nd floor, but them missing is the important part. Since even with debug commands (via mods) or trainer there is no "ghost mode" to phase through walls, we instead activate godmode and/or deactivate fall damage in the trainer, and instead jump down the elevator shaft. This part could also be accomplished via debug commands, the next step will likely be the issue with only those, though. At the bottom of the elevator shaft, crawl into the space underneath the elevator you want to exit from - then activate "fly mode" in the trainer, which places you hovering mid air. Another command lets you adjust the flight height, shifting your character upwards - and can actually push you upwards through the floor of the elevator into the cabin. Then just deactivate all the trainer cheats and progress normally. I did not run into any other issues after this and could finish the quest with the rift modulator in my bag.