Will do some more tests when I get home. Could you make a video of what is happening with OBS? Its free and way better than old fraps or bandicam. Find it here:
https://obsproject.com/download
Are the zombies getting stuck in the stairs?
Are the zombies getting stuck at the bottom of the stairs?
- Might be that the zombies are slightly inside the floor, try raising up them a little bit.
Are the zombies getting stuck at the top of the stairs or on the gantry?
- Might be the gantry segments, will test soon. I remember some with "hollow" parts had collision issues sometimes. Maybe try a different gantry or floor segment.
Are the zombies choosing to run underneath the gantry rather than up the stairs?
- Change your level design to accomadate the zombies. Place items near the stairs/under the gantry to encourage them to use the stairs. Ill play with this later and see if I can come up with a clever solution for us.