this apparently was my problem too.
happy orbx user for years on my other pc (had p3d and all scenery on the ssd). got new pc on tuesday, fresh install of everything, so tried to be smart about it (old pc's ssd was almost full by the end) so, p3d installed to ssd.. figured i'd get cute and use the new library function and put all the scenery on the big 2tb hdd .... then ran into these annoying artifacts.. just like shown above... so after uninstalling, reinstalling to the main directory, verifying and syncing, it finally appears to have resolved itself. it looks like i remember. I think the main thing today was finding this thread and seeing that i needed to move the libraries to the main directory not just the global base and openlc's.. then re-verifying etc.
so i cant use the library function to offload scenery off my ssd, but i really dont care, i'll live with it. its faster anyway