I work at a dealer, I can't recall a term like "mechanically set" being thrown around, and I've worked on lots of these tops.
Your complaint seems to be just the hardtop, can you tell exactly what isn't latched? There is a latch on all 4 corners (2 on the top of the windshield and 2 on the rear corners).
Any idea yet on if the soft top is operating?
It may be a good idea to have the top system inspected by the dealer, or an independent shop but only if they say they are very familiar with the 1990 through 2002 SL power top system.