Object has weird shadow lines in buy mode

I think this can be solved by just clearing your game thumbnails. Sometimes this happens to me too when I create custom cc, it looks odd but I think it's just our own game files tricking us. Usually I solve it by deleting cache thumbnails either via Sims 4 Studio or just in my sims folder itself. If for some reason it still isn't working there is always the option of creating your own custom thumbnail instead of letting it be generated by the game or S4S. If you need any further help with this please let me know and I will try to help you with the best of my abilities.