1. Rear trunk wiring harness will bend and fold when opening or closing the trunk lid which lead to the wiring broken after long service time, causing open circuit problem.
2. Rear trunk rubber or wiring harness sleeve are made from rubber which will aged eventually. Poor seal will cause water go into trunk during rainny day or after car wash which will corrode or oxidize the wiring harness.
Suggest to repair at workshop after discovered the issue. Need to engage a professional to identify the problem and proceed to repair or replace the wiring harness.