I saw this in a post from 2019: https://forums.daybreakgames.com/eq2/index.php?threads/control-undead-mercs-constant-curing.592371/ Listed under resolved. Well regardless, the bug seems to have popped back to life. I have an inquisitor merc (Stamper Jeralf), and it's just a neverending repeat of curing messages. I have not tried another merc class or character that can cure. It has happened with absolutely every mob that I've charmed, so it's easy to reproduce. Grab a necro with Stamper as merc, use control undead on something, and watch it unfold.
Yep this happened with the inquis merc my necro was using the other day - the Celesital guy from VoV. Super annoying.