Down staircase made me descend several strata at once

I was on stratum 4 fighting an esper hunter who summoned a space-time vortex next to me (near the up staircase). I killed him, then went back up the stairs to wait out the vortex duration. When I went back down the stairs from stratum 3 to 4, the game made me immediately descend multiple floors all the way to stratum 9.

Mods installed: QudUX (with manual fix)