Any chance you have continue on error in some steps in TS? If not, try to find, will smsts.log contain any 0x19c type of codes which should reveal you the exit code and reason why IPU did not executed. There is also an small app for IPU troubleshooting - it is basically small setup program which will analyze your current setup and reveal you the reason.
Also I remember a year ago there was a huge problem with Conexant audio drivers preventing IPU to succeed, but it did fail then.