Managed to generate something similiar, but it did take quite a few tries:

As far as I can tell the problem is that the "air vent/duct" from the lab tile is not in line up (and does not connect) with those of the other tiles. This combined with the "air shaft" location of the T-Tile leads to the junction with the spawn point being cut off. Either align the shaft of the lab tile "correctly" or add/move the air shaft on the T-Tile so it connects to the rest of the vent/shaft network.
Misaligned shafts from lab:

Move/place additional air shaft on T-Tile:
