I think you are fine curing the loan the first time it is discovered "and putting in procedures to avoid it happening again". I think you have not cured it if you repeat the pattern on a regular basis.
Unless I am confusing your situation with another, I think, in order to avoid an impermissible forfeiture under 411, he should have been receiving in-service distributions starting at the point in time his actuarial increased benefit exceeded the 415(b) limit. I believe there is a statement in the DB LRMs to that effect, if not published elsewhere.