Took my 2014 GX in for 5k miles service even though it has only 1K miles (bought it in Nov 13). The service write up person recommended oil change (10K service). I was cool with that because I still believe in first oil change in 1K miles when the car is new regardless of what car manufacturer says.
After 1 hr waiting, the shop manager told me that my GX needs to stay longer because they discovered a small leak in rear main seal. From what I read on the internet, it is a time consuming repair.
I don't drive the car much, 1k miles in 7 month. It is parked indoor most of the time. I do drive it 5-10 miles every 2-3 wks to cycle the car. I also use battery tender to keep the battery charged.
I was surprised that this happened. My friend's 2014 GX (he bought it because I told him Lexus is much more reliable than his LR3) had his back up camera replaced at 3K miles.
The term, "Rear Main Seal," refers to the seal at the rear of the engine where the crankshaft is exposed to the fly wheel. Many people use this term to mean other seals. I do believe the OP is refering to the definition stated here.