Specific to '89 but I suspect universal application...

The latch holding the folding table into its cavity in the wall needs
periodic oiling.  If you examine the latch mechanism mounted on the
underside of the table, there's a spring-loaded ring.  If you press
that toward the table, a little pointed thing emerges from a slit in
the post, with either two points showing or one point just barely
showing.  In both conditions you must be able to easily rotate it
clockwise with your fingernail, or you're in danger of it hanging up
and refusing to disengage from the wall.

Yours,
David