This is an old bug and your "fix" is just a coincidence. Aric's mod had a bug as part of the revised sexual feature construction that resulted in data corruption by appending possible penis sizes for babies onto the penis size list for all uses. Your fix was simply waiting for a new male or futanari person to be created and further corrupt the list.
Line 75 of ".../files/scripts/assets.gd" should end with ".duplicate()". Which when fixed should look like:
temp = globals.penissizearray.duplicate()
The file can be edited with any text editor if you don't change any whitespace(spaces, tabs, or newlines), or a decent text editor like Notepad++ or Sublime Text 3.