Mobs not spawn

I have some problems have a long time with my account. Inst the device because i have 2 and both of them i have that problem.
The first problem appeared on my account was the Mob sub-boss/miniboss Giant Boar desappeared and never respawn again. Maybe i've never seen others sub-bosses/minibosses because of that problem.
My second problem is about normal monsters dont spawn correctly. Every time i tryed farm something where dont have too much players to help killing mobs to respawn to kill some mobs my team party didnt start the aggro, but the maps with no players i cant farm because they dont respawn correctly.

Can my problem possible be fixed? ;-;
Thanks for listening! I am looking forward for the answer.

 

Your best bet is to re-enter the map.

 

there's a limit to how many mobs can be on the map.
there are 3 things you can do:
1 - kill the other mobs
2 - walk away. mobs disappear when you are farther than 24m. (not possible on small maps)
3 - leave and re-enter the map. this will reset everything.