[E. Albright]

Originally posted by Taqwus:
Check whether the Eternal Knights have a 'recuperation' flag. Recuperation heals diseases like any other affliction, although it may not be fast enough to save the unit in all cases.

Couldn't have been that. I wasn't clear enough. After a lengthy delay, the diseased, regenerating Knight was still infected, but the disease was its sole affliction.