Occasionally can't find first gear - 2005 Audi A4 Avant 1.8T

[DickyC]

or second. It's an 87,000 miles Quattro in reasonable nick. It's a 6 speed manual and every now and then I can't find first or second. The gearstick is in the right place in the neutral plane but won't go up or down into first or second. And then, equally mysteriously, it goes in. On the worst occasion, I turned the engine off, put it in reverse, put it into first (an old trick from cars with no synchro on first), restarted the engine and set off. It took time. I was Mr Popular.

It feels as if there's an obstacle loose among the selectors but there probably isn't.

Any ideas? It's my third old 6 speed Quattro but it's the first one to do this.