On a recent call to a piano in a customers house we were responding to a problem with the soft pedal in their Yamaha upright piano. The pedal had stopped working mysteriously over a weekend and the owners had no idea why as up to then all was well. When we removed the front panel we immediately saw that the rod was out of place and would not lift the hammer rest rail.
A simple moving forward of the rail and we reinserted the rod through the rubber hole in the lift and slightly adjusted the rocker in the bottom of the piano. It turned out that there had been a birthday party in the house for one of the children and they had access to the piano and were using the pedals without playing the piano and letting the piano off suddenly instead of controlling its use which you do when playing.
The pedal had bounced the rod out of position and as a result the pedal would not lift the rail. This is something we come across from time to time as rods move out of place if the pedal is let go with some force. Pedals and their mechanism are designed for slow gentle foot control and do not respond well to being bounced of misused and as in this case required an onsite visit to fix simple as the problem was. So it is good to remember that even small children can create problems for pianos if they are not shown how to treat the piano properly.