I've had this issue a few times now. I save out my project with it looking normal with no shading issues, but then when I reopen the project the meshes all have this shading/UV error maybe? Can anyone tell me what causes this so I can avoid this happening further? Thanks!
@Sage It was multiple UV sets! (Whenever I'm combining and uncombing those seem to get created in the background a lot.) Thanks for your help. Thanks to everyone who also gave their input.
could it be a glitch with the lambert? Perhaps reassign the default or a new lambert? Otherwise my other guess is viewport display setting are messed up.
If it's not a flipped normal issue, check that the model doesn't have multiple UV sets. Sometimes you can get a situation where map1 doesn't have all the uvs and you can other uvsets that have all your uvs in there. This sometimes happens when combining multiple objects together and extracting parts as needed and…