Ok, there's a fix ready!
Go into your
C:\Sex Sim\Runtime\_aData\assets\textures\ folder and look for the file called "
tex_char-Petra.sexsim" -
DELETE that file.
Then, start Sex Sim, and at the bottom of the login screen, check the box to do a "
full file check", and continue logging in.
During the login process it should download the fixed texture set for Petra, belly button and all.