2004/186k miles and FSH. I've had it for c8k miles without any issues. Driving gently today the transmission shifted through a couple of gears (as normal) and then, what felt like a jerky shift, lost drive completely at about 40mph. The engine revs dropped to tickover. While coasting, I manually shifted from D to N and back again a few times but it would not reengage Drive. I pulled over, put it into R which engaged fine and then back into D, and it engaged Drive as if nothing was wrong. Is this a common thing that I don't need to worry about or a known sign of major transmission failure to come??