I notice this happening when the main fallout.exe is only taking about 2.6GB in memory (I have 2 monitors and Task Manager is running on the 2nd) which would seem to confirm the 4GB patcher IS working. I'm having the typical issue when running low on memory - fast travel to a new area, or just spend a long time wandering around, and I start getting bad textures and/or the 'red exclamation point' signs.
I decided to break out FNV after a year or two off for F4.I'm fairly well experienced with modding the game and the common problems, though this is my first run with Windows 10. So, I know this may not be the right forum for heavy duty troubleshooting but maybe this is just something DUH stupid I haven't come across before.