[HELP] Can't kill costum mobs

Can't kill gremlins and some other mobs like the custom ones but I can kill most of the other mobs, if I spawn mobs in the same place I can't kill them :/ weird, no geodata anyways. Any1 with the same problem ? Or know the solution?

Check on DataBase the "npctype" of these mob, maybe it is wrong

L2Monster, I copy pasted the mob from table npc changed the id exp/sp/hp/patk/pdef/mdef

Here's the error when I attack it:

WARNING
java.lang.NullPointerException
at net.sf.l2j.gameserver.skills.Formulas.calcPhysDam( Formulas.java:1280)

at net.sf.l2j.gameserver.model.L2Character.doAttackHi tByBow(L2Character.
java:1058)
at net.sf.l2j.gameserver.model.L2Character.doAttack(L 2Character.java:947
)
at net.sf.l2j.gameserver.model.L2Character$AIAccessor .doAttack(L2Charact
er.java:3673)
at net.sf.l2j.gameserver.model.actor.instance.L2PcIns tance$AIAccessor.do
Attack(L2PcInstance.java:315)
at net.sf.l2j.gameserver.ai.L2PlayerAI.thinkAttack(L2 PlayerAI.java:207)
at net.sf.l2j.gameserver.ai.L2PlayerAI.onEvtThink(L2P layerAI.java:315)
at net.sf.l2j.gameserver.ai.L2CharacterAI.onEvtReadyT oAct(L2CharacterAI.
java:653)
at net.sf.l2j.gameserver.ai.AbstractAI.notifyEvent(Ab stractAI.java:386)
at net.sf.l2j.gameserver.ai.AbstractAI.notifyEvent(Ab stractAI.java:336)
at net.sf.l2j.gameserver.model.L2Character$NotifyAITa sk.run(L2Character.
java:2458)
at java.util.concurrent.Executors$RunnableAdapter.cal l(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unkn own Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$S cheduledFutureTask.
access$301(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$S cheduledFutureTask.
run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run Task(Unknown Source
)
at java.util.concurrent.ThreadPoolExecutor$Worker.run (Unknown Source)
at java.lang.Thread.run(Unknown Source)