I have paved my own house mod exterior courtyard with "SOVintFloor001 (0003e6c1) floor tiles. Created navmesh just above the surface which work as it should BUT both PC and follower NPC sink up to their ankles when they walk on it. Can anybody tell me please what might be the cause? TiA

I'd venture that the mesh isn't quite lined up with the texture. This is sometimes seen when an object is scaled up too much (e.g. 8x original size).

Thanks for your answer RE. Tiles are actually half size (reduced to 0.5000). You think that it might also cause this problem?

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I can't say I've seen that happen with reduced model size. There is definitely something odd going on. Sometimes, when the game is a bit stressed it will load the mesh and the texture in two different places. I've seen this happen with Mannequins, but it does not happen very often - and I've never seen this occur with statics.
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If you select all the tiles and draw a collision box on them, I think this might solve your problem.
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