Sorry, I only halfway answered your question.
The problem is, the tail light buckets get 'soft' over time and usage. That allows each bulb to twist in their sockets and NOT connect to the power source.
Hi wallew - I just got the notice today, that you had added a reply 4 days ago. So I'm a little late in responding.. Thanks, for taking the time to explain what happened. Now I'll know what to watch for..