I’ve playtested this three month old version and I don’t see this happening even by going up and down the stairs.
Besides, this was only when I added the experimental 3d levels, which the game specifically says dude this fucks shit up and doesn’t even work why is this option even here. In the 2d version it just told me “nope, there’s only a downstair here.”.
So I don’t really see what the whole problem is, unless they reinvented the wheel in the last few months and fucked something up. Even then, 3d z levels is beyond fucked up. Zombies can climb 10 stories buildings and just waltz on your roof to smack your ass in five seconds, because they just don’t care yet and treat that shit like sidewalk.