Well the relay harness has the potential to cause both of thee ballast failures. We all know how sensitive ballasts are to voltage fluctuations, and if this relay box has been having problems, it's possible is wasn't providing stable voltage and led to these failures. I need to look back and see which side's ballast died the first time.

This relay harness has always had a weird quirk, when the lights turn off, the driver side always turned off first, then the passenger a half second later.