Mobs don´t massive spawnig in mob farms in server

Hi, i create a minecraft server in 1.14.1 and udapted in next version, there is a heavy world, explored, maping, masive farms, etc. is only 2 player there server, 

i found this bug when i build a mob farm in the overworld. mobs not spawns how it should be is only 20 entity, between the majority are peaceful, 2 or 5 are ostiles mobs. if i go to the ground is still the 20 entity, and if i go a place is aldredy loaded, for example the base, is all good, the average of entities between 50-70.

i doble check if doMobSpawnig is in true, or reset the server, but evething is the same.

i don´t know what i can do, i can,t reloand every chunk to dispawn ever hostile mob to see if works. i only left to leave it as a bug.

Pd: in a singleplayer world is works rightly.

Pd2: in the server i use portals traveling, thats why mobs not dispawns in the leave chuks

Pd3: if it is needed my server world, ask for it, i have no problem