Problem/Bug Worldguard - Issues with Priority/Parenting Regions

Hey Guys...

my issue comes up one setting multiple regions (one big with some smaller in it) and starting to set the flags "deny-spawn" with a list of all monsters for the big area.
Now i tried to set the smaller regions in the big one to let spawn only one of the whole monsters (f.e. Creepers or Zombies).

at the end after trying serveral hours with /rg setparten big-region small-region or setting priority i can not get the smaller regions to let the mobs sapwn, unless i set the whole big-region to let this types of mobs spawn...

Using: Minecraft 1.14.3 Server files an the latest Release of Worldguard/Worldedit

Someone could know a deal with this? (sorry if my english isn't that well...)