Close spawns is one of the most notorious issues of this game and since the inception people have been complaining about it. Oftentimes people refer to this as the "teleports issue", however, teleports, if disabled, address only one side of the issue as new zeds, that replace those you just killed to fill up the maxmonsters on the map again, can spawn very close to you, a phenomenon which is commonly referred to on forums as zeds spawning out of one's ass or zeds spawning on one's head.
Playing the multiplayer games partially alleviates this problem as there are less spawnvolumes that are unobserved, this may explain why you didn't notice it.
The solo video some dude recorded and you featured in the steam workshop item for your map demonstrates the issue clearly several times. It's clearly noticeable at 0:52 (he doesn't curse, but gets surprised by the spawn on the left), 3:59 he exclaims "where they are coming from" (they come from the attic because the min spawn distance is too low) and so on.
You can also check my HoE+ run, it's full of it along the borders:
Of course, if you play below HoE+ and/or never have to deal with "last man standing scenarios" and kiting scenarios this issue isn't as annoying and frustrating to deal with, but on HoE and higher it's a plague and I believe #1 reason people eventually get fed up with this game and leave. I believe TWI shot themselves in the foot by doing it this way, but it's something the map makers can address on some maps at least, that's why I'm asking.
