DA* 50-135 focus issue
As far as sending your for repair I would say don't bother. You are likely to get it back a number of weeks later with a note saying "no fault found".
Peter
My Flickr page

Is the problem with AF at low light? It's been a problem with my lenses and the lens hunts (not limited to DA* glass either). If SDM works on other occasions it doesn't sound like the SDM motor but maybe the sensitivity of the AF sensor...
Battery maybe?
Let's hope you get to the bottom of it by the time the gigs come around.
Z-1p, K-1, P50
F50 1.7. FAs 24, 35, 50 1.4, 85, 135

Metz 45 CL-4, AF500FTZ. AF540FGZ.
Some Mamiya and some Nikon
Is the problem with AF at low light? It's been a problem with my lenses and the lens hunts (not limited to DA* glass either). If SDM works on other occasions it doesn't sound like the SDM motor but maybe the sensitivity of the AF sensor...
Battery maybe?
Light level made no difference. What I can't understand is why it would hunt only at maximum zoom or thereabouts. Knock it back a few millimetres and it would work normally. I made sure to test it with full batteries. My old Peugeot 307 did the same as your VW. Luckily, the problems disappeared when it spontaneously combusted in a car park

Pentax hybrid user - Digital K3 & K200D, film 645 and 35mm SLR and Pentax (&other) lenses adapted to Fuji X digital
Fan of DA limited and old manual lenses
Aero
Member
Aberdeen (Scotland)
I'm concerned (and fairly confident) the problem will return when I'm relying on the lens later this year at some music gigs. It strikes me there's no point sending it in for repair while it's working properly. I suppose I could describe the problem and hope for the best, but this wouldn't be ideal. Any advice on the best way forward? I looked into switching it to screw drive but all the information on the net was quite old and some of the required software doesn't seem to be available from a reliable source any more. I'd appreciate any wisdom you can offer.