Have seen some PAPI problems in cold climates as well(if that is any concern on this forum
). Snow clearing vehicles operated improperly can cause faulty display signals if the snow or the vehicle strikes the PAPI unit.
As well, in very cold temps frost can form on the PAPIS causing the red to appear pinkish which could be interpreted as being high on approach. A solution to this was a requirement for airport operators at remote airports with lighting that is not continuously in operation to leave the PAPI units continuously operating so that heat would prevent frost buildup.
From the FAA...
"This is to advise airport operators of the possibility of light signal interruption from PAPI units not operated continuously, e.g., those units activated through the use of pilot-controlled-lighting (PCL) systems.
Because external PAPI lenses, used to improve light signals, are exposed to ambient weather conditions, the possibility of dew and/or frost forming on the outside of the glass becomes a concern when the units are not operated continuously. In particular, a PAPI unit operating in the “off” mode for an extended period of time during the evening hours could accumulate a level of environmental contaminants (e.g., dew or frost), which may not dissipate sufficiently to ensure correct light signals after pilot activation.
To preclude environmental contamination of PAPI lenses along with possible lighting signal interruption associated with limited dissipation of any dew/frost FAA recommends the following:
At airports where PAPI units are activated when needed and thus are not operated continuously, change airport lighting circuitry to ensure PAPI’s are preset to operate continuously on a low power setting, either 5 percent or 20 percent of full intensity as necessary for local site conditions."
Also....
https://www.tc.gc.ca/eng/civilaviati...98002a-180.htm