Why does my car keep slipping out of 3rd gear?

I own a 2011 BMW 118d and recently the gearbox kicks me out of third gear but all gears are working fine with no issues. I am just wondering what it could be before I start spending money on unnecessary things which are irrelevant?
The reasons for the gear to jump out on a manual gearbox could be that the engine/gearbox mounts are worn (more so if you are off throttle), the gear selector linkage is worn or the detent spring /ball (inside the gearbox) is weak/broken. It's best to get a reputable garage to diagnose the issue and go from there.
Answered by Alan Ross on

Ask Honest John