The current build for V10 is 1340 found here:http://tcmacforum.imsisupport.com/index.php?topic=2660.0
Build 1321 has some issues, I can't remember what, too many to keep track of.
The only issue that I am aware of causing lines in rendering are two surfaces on top of each other. Say you have a wall surface that is rendered blue but you don't want the entire wall that color. You place a cover surface on the wall and set that to green. When you render it you will get green and blue stripes. The problem here is the program is having a problem determining which surface is on top, sometimes the wall is and sometimes the cover surface is, the fix here is to move the cover surface away from the wall just a hair.