CAD Library or Substitution Issues
We recently ran across an issue out on the shop floor that was most likely due to the components library in the CAD package. A QFN part was sent for this assembly but the land pattern on the board was just a bit too big. The QFN pads would not reach the pcb solder pads.
Most likely, the designer accidentally selected the library part for a QFP variant of the chip instead of for a QFN. The parts are pretty similar in size if you exclude the leads on the QFP package. It's also possible that someone accidentally purchased the QFN variant when a QFP was called for.
Just one more thing to add to your design-check.
It's just over that next hill...