Update: cleaned up some wiring and grounded each light at the housing but the primary issue was that my tail light housing was not holding the bulbs securely and that was creating my grounding issues.
Lesson: buy good housing - I replaced with OEM housing and things seem to be working solid now.
My 76 FJ40 (completely re-wired about 2 years ago) started having the below issues recently, I believe simultaneously and all of a sudden. Wondering if you can suggest where I begin looking to identify the issue as I assume they are all related. REALLY don't want to take it to...