On returning from the Santa specials on Sunday, both crossheads were found to be hot. The LHS was stripped down yesterday and the white metal on the bottom slipper was found to be worn. It is being re-mettaled in time for the Santa's next visit.
The RHS will be done next week.
The cause is unknown , but a lack of lubrication is obvious. The design, 100 years old as it is, supplies good lubrication to the top slipper, less to the bottom one.