Hi all
I am 5 boxing with a priest and 4 locks. I have 5 marcos on each toon to switch between them
/cleartarget
/clearfocus
/target [target=toon1] ---- toon2--toon3--etc
/focus target

I than use another macro for every toon to assist the the toon I switch to
/target focus
/follow
/assist focus
/stopcasting

I have this castsequence macro for my warlock DOT
/petattack
/castsequence reset=target/combat Curse of Agony,Corruption,Life Tap,Drain Life,Shoot

When I attack, 4 of my warlock will cast the first spell, but one will only cast the first spell in the castsequence and then stop.
IF I am fight 2 or 3 mobs. I can switch to the other mob. The same toon and its' pet will just stand there and do nothing while my 3 other toon will reset the spell sequence and start casting spells again.

I also have a different marco to sent the pet in to attack by itself, If I press the button this is bind to, The same toon pet will attack, but he will not cast any spell.

No very sure why this is happening. ?(