Herald of Purity + Infernal Legion bug

I'm running HoP + IL Minion Instability, and somehow I frequently (at least once every 2-3 maps) end up with Sentinels of Purity that don't degen, sometimes more than one at a time. The skill icon on my skillbar and the buff icon that shows how many Sentinels I have both show that HoP is supported by IL and additional Sentinels that I summon degen as expected. If I unsocket and resocket IL, the Sentinels immediately start degenning. I haven't noticed any pattern with it happening with particular zones or monsters or anything.