I was in Salt Lake City at the Library in November and encountered the same problem, mostly. I asked about this at the British reference desk and received an explanation. It seems that the On-line catalog is different than the old in-house catalog and some of the parish register films ARE NOT in the new on-line catalog. They are there in the old DOS version, in-house catalog. Not much help if you are not in the Library!!!

I believe the explanation I received was something along the line that these were missed when they did the new catalog. I am a bit hazzy about that now some three months later
I have the batch numbers for many of the parishes if that will help, but not all.

I cannot address the IGI problem but have not encountered and problem with it. Can you be specific about information is not available in the IGI?

Richard