I always repair or replace mine if I find water in them. Some have WEEP HOLES and was installed in the wrong direction. Some have dried up sealent applied.
Letting water stay inside the marker lights will eventually cause damage to the light assembly or the wiring and may drip water inside the trailer coming through the walls where the wiring is installed.
One extreme situation I had was the large 8-inch scare light lens was installed wrong and the weep hole was on the top. It had filled up with water up to where the wiring went through the trailer wall to inside the trailer. I had water dripping inside a ceiling mounted cabinet and desk top below it. Scratched my head for a bit as to why it was half filed up with water and the identical one on the other side of the trailer didn't. That is when I noticed the weep was at the top of the fixture instead of the bottom. Lucky I didn't get any sustained water damage on the inside of the trailer.
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS