Malzahars Malefics sometimes dont cash kills in properly

Ive noticed that a near 1 to 4 ratio for s Malefic Visions will kill the minion and give exp but wont give the gold.If I throw it down and the minions only attack it wont cash the gold if Malefic Visions does the kill, it also will do this on occasion with his basic attacks. Now either a the minions are getting really lucky or the Malefics slightly bugged.