I’ve also discovered that this problem manifests itself when only using one UV tile. If the UVs exactly fill the default 0-1 space, any values which are exactly 1 will be changed to 0 when imported.
RC certainly isn’t the only software to exhibit problems like this and it’s generally good practice to scale UVs down slightly to avoid it. However, it’s still an issue which can result in long processing times resulting in failed textures.
The attached image shows what happens to the UVs in this case. The top is before the model is imported, and below it the model when exported from RC. The reason for the red is because the error causes the all UVs to overlap, which is obviously a bad thing.