I am aware of at least one large hardwood lumber company here in NC that uses the lignomat control system (there may be more).  If my memory serves me correctly, I believe they are using pins to measure MC (measures electrical resistance to estimate MC) of the sample boards.  Rather than the more common dry bulb / wet bulb, this lignomat control system is using cellulosic wafers to measure the EMC (equilibrium moisture content) conditions in the kiln.

If you are running a traditional Lignomat kiln control system there are only a few things that will shut your kiln down.

Loss of EMC/WB or DB readings on both sides (can not regulate what it does not know)

Fans running in wrong direction (only seen on installations or after reworking the MCC or VFD's)

Damaged PLC or control modules.

These are the most common. Look at the kiln histories for errors, the errors may go away on the screen if the kiln is down for a while but will be recorded in the history.

If nothing is smoking you can swap PLC's and other electronics and track down the problem. Call Lignomat  for support, spare parts are on hand even for old control systems.