Two that come to mind...
1. The final episode of Super Password, when Betty White is unable to help her partner win the CA$HWORD, she throws the magic toaster and it breaks.
2. During one Showcase Showdown, the player had 30 cents and spun again and landed on 70 for $1.00. In his excitement, the player was thrashing his arms around and he hit and broke the "7" on the wheel. Drew kind of laughed it off and fixed it. I know had Barker been there he would have said "I'm glad you won $1,000 because that's how much it's going to cost to fix our wheel!"