Hey, don't know if anyone is still listening but I had the same problem and we're in A19 now. Documented it on video here https://streamable.com/qx0p50 except without even using a POI and they still spawned inside. Then made an official bug report of it here. If any of you would like to add your weight into it then it'd probably help them recognize this for the serious bug that it is.
https://community.7daystodie.com/bug-test-1/under-review/bloodmoon-zombies-spawn-within-lcbbedroll-zone-r1740/