Last week I sent back the Zeiss 16-80mm lens I'd bought the week before through ebay, because the front barrel was loose and flopping around. Only by a millimeter or so, but still loose enough to let me feel the 'clonk', through the camera body.
So this morning I put my old standard 50mm f1.7 lens back on & went to take some pictures in the garden before leaving for work. I just imported them into lightroom & after examining some at 100% magnification, began deleting them because they weren't sharp. After I reached the 3rd image I realised it wasn't the camera that had failed to focus, but that the 'standard' minolta lens was simply much less crisp than the Zeiss I'd returned, and I was binning the images because they simply weren't at the same standard I'd become used to.
Looks like it will need replacing like for like then.