So I was giving my car a 90k servive today and found a bunch of swarf on the gearbox drain plug.
The 'box has worked perfectly until the other day when it was quite tough to pull it out of 3rd gear. But that's only happened just the once.

I dont recall crunching any gear changes, but I've only had it for 5k miles. Who knows what the previous owners were like!

Anyway, do you think I should investigate this further considering it seems to be working ok?

 

Looks like quite a lot of swarf, how long since the last oil change.
It's full of moving parts that mesh and engage with each other so you are always going to get wear.
As long as it drives ok and sounds okay I wouldn't get too worried.