Ok. I played through 10 rounds on solo.
1) I noticed that the smaller doors when welded and then destroyed by zeds --these doors still appear and are solid to players but zeds can walk through.
For example, the small door to the left of elevator broke but remained and was solid for me (but zombies walked through the solid-looking broken-down door).
2) Down the long hall from elevator forward towards the red lighted room, the small door on the left also had the weld broken. That door, like other small doors was still showing, it was solid for me, but zombies walked through it.
3) The smaller room to the right of elevator with that small door and big window --that smaller door seems to be a problem for zombies to break down. A few got stuck there or seemed to be clueless as to whether they should just face the door (while moaning and gesticulating) or whether they should beat on the door.
All in all, the map feels very much like the bioticslab I was loving in KF1. It even had that same size of hallways and walkways almost everywhere. I really enjoyed it. I was hoping to get on a server with some testing people, so maybe later tonight. I took a long fraps video of my play, but since it was only on normal I'm not going to post it any time soon.