I'm not too familiar with 401(k) plans so I apologize in advance for my ignorance. Say an employer makes matching contributions in excess of the plan's limits for matching contributions (i.e., employer matches more than the "50% on the first 6% of compensation" as specified in the plan document). The plan's service provider has taken the excess match and allocated it to a forfeiture account. Are there any problems with this type of transaction? What potential issues, if any, does this create for the plan? Any insight would be greatly appreciated.

That's the way we do it. But keep in mind, those are "forfeitures" in the sense that they are unvested money, to be treated as the plan document dictates (reallocate, cover match, fees, etc).

I like to call it suspense money, which the plan uses to reduce its next contribution check.