Wallpaper Size Error....HELP PLEASE!!

Heya, 

I have made several wallpapers before and never had any issues. I have gone into S4S to make some today at the with image dimensions saved out as DDS at 256x512px (original 256x768 for small wall) but I keep getting the the below error which says calculated size doesn't match...

I thought maybe it was the file, so I went back and selected one of the wallpapers I have made previously (that i know definitely worked with no issues previously) and got the same error again!

Have the size peramiters changed or something? I am unable to make anyhing :( 

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The Sims 4 Studio - Version 3.1.6.3

System.AggregateException: One or more errors occurred. ---> System.Exception: Calculated image size does not match actual size.

at S4Studio.AMDCompress.AMD2Bitmap(AMD_TC_Texture destTexture)

at S4Studio.AMDCompress.DecompressImage(Stream stream, Boolean fast)

at S4Studio.AMDCompress.DecompressImage(Byte[] buffer, Boolean fast)

at S4Studio.TC.ConvertData(String src_ext, String dest_ext, Byte[] convert_d, Boolean requiresAlpha)

at S4Studio.ViewModels.BuildBuy.WallTextureBase.Import(String file)

at S4Studio.ViewModels.BuildBuy.WallSwatchContent.<>c__DisplayClass4_0.<ExecuteImportTexture>b__0()

at System.Threading.Tasks.Task.InnerInvoke()

at System.Threading.Tasks.Task.Execute()

--- End of inner exception stack trace ---

---> (Inner Exception #0) System.Exception: Calculated image size does not match actual size.

at S4Studio.AMDCompress.AMD2Bitmap(AMD_TC_Texture destTexture)

at S4Studio.AMDCompress.DecompressImage(Stream stream, Boolean fast)

at S4Studio.AMDCompress.DecompressImage(Byte[] buffer, Boolean fast)

at S4Studio.TC.ConvertData(String src_ext, String dest_ext, Byte[] convert_d, Boolean requiresAlpha)

at S4Studio.ViewModels.BuildBuy.WallTextureBase.Import(String file)

at S4Studio.ViewModels.BuildBuy.WallSwatchContent.<>c__DisplayClass4_0.<ExecuteImportTexture>b__0()

at System.Threading.Tasks.Task.InnerInvoke()

at System.Threading.Tasks.Task.Execute()<---

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