separate 5500s for solo(k) and DB plan?

I have a client with an individual 401(k) that has not reached the 250k threshold in that plan; however, he does have a DB plan for the same business, that is over 300k. The person who administers that plan and files that 5500 stated that I should be filing a 5500 for the 401(k), due to aggregated assets in both plans. He has not made contributions in several years, as the business was dormant. Do I need to file a 5500 for the 401(k)?

And a filing was due for each plan the FIRST year that COMBINED assets exceeded $250,000, so make sure there aren't any delinquent filings requiring correction.

Yes you do!