I have the same problem with my server.
But now it's fixed.
The problem is with the status effect.
Open skill.c file and find
case UNT_ZENKAI_WIND: sc_start(ss, bl, SC_SILENCE, sg->val1*5, sg->skill_lv, skill_get_time2(sg->skill_id, sg->skill_lv)); sc_start(ss,bl, SC_SLEEP, sg->val1*5, sg->skill_lv, skill_get_time2(sg->skill_id, sg->skill_lv)); sc_start(ss, bl, SC_DEEPSLEEP, sg->val1*5, sg->skill_lv, skill_get_time2(sg->skill_id, sg->skill_lv)); break;
Zenkai also cast Deepsleep status which nightmare card only gain immunity to Sleep Status. Not Deepsleep
So just delete the last line and it will looks like below
case UNT_ZENKAI_WIND: sc_start(ss, bl, SC_SILENCE, sg->val1*5, sg->skill_lv, skill_get_time2(sg->skill_id, sg->skill_lv)); sc_start(ss,bl, SC_SLEEP, sg->val1*5, sg->skill_lv, skill_get_time2(sg->skill_id, sg->skill_lv));
And recompile.
So Zenkai will cast Silence and Sleep status which player can use Nightmare card to gain immunity to sleep and use Green Potions to Cure the Silence status.
Just for share. Thanks a lot.