Gearbox problem (manual)
It happened once before, couple of months ago, and I ignored it thinking it was a one off. But today, I've had difficulty getting 4th and sometimes 3rd gear. Normally it's changing from 3rd to 4th, then when it physically won't go into 4th I try for 3rd again and it's either very stiff or won't go. The others are usually ok.
After a bit of selecting other gears, 4th usually 'comes back', although stiff. I know the clutch is ok (no slipping, bite is fine, other gears are normal), so what could it be? Linkage? Clearly this sort of thing isn't going to go away, and it seems like it's got worse.