"undercover" is one of those episodes most universally despised by columbophiles, it contains more than its fair share of grotesque moments (like Peter Falk's bare pasty legs while changing into a mafia don disguise in the back of a squad car....)
many of those made from 1989 didn't fare as well as the earlier episodes because the shows were lengthened to 90mn (2hr slot with adverts) to get more advertising revenue, while earlier shows were 75mn (90 mn with adverts) and were faster-paced. a classic of this was the Tuba scene in "Sex and the Married Detective" - whilst amusing enough, blatant padding.