I completed a 115km back country gravel event in Corner Brook, Newfoundland last week which was on terrain everywhere from tame to knarly, with some rain, mud, puddles, water crossings...
My RD didn't suffer from water ingress, but at the end of the event my watts were not making sense. When I got home, found that the two jockey wheels were completely locked up. They use 626Z bearings, which have metal shields and are not sealed like their 626RS counterparts.
I've sourced some bearings at the local Wajax but also have a request sent to LTWOO to warranty the jockey wheels. I've got maybe 1000km on this group since May.