Not sure if its a bug, Mobs resetting, not following (NO BUG)
 

[00:04:38] INFO ========================================== =======
[00:04:38] INFO Project Revision: ........ L2s [23110]
[00:04:38] INFO Build Revision: ......... 11867
[00:04:38] INFO Update: .................. Classic 1.5
[00:04:38] INFO Build date: ....... ....... 2017.10.23 00:27
[00:04:38] INFO Compiler version: ........ 1.8.0_151-b12 (Oracle Corporation)
[00:04:38] INFO = ================================================

Any mob is resetting, making it impossible to group several mobs in certain places to level up in group.

Video for demonstration in Antharas Lair

https://youtu.be/6hh1f6UAzJY

mobs went a long distance, this is normal reaction

Configure in ai.properties:
Closed.