Understanding Society User Support

I'm trying to use the religion data from Understanding Society, and there's a few variables for which there isn't an explanation given online as to why some of the sample have been made inapplicable. Additionally, there are some variables where there is a universe given, but the number of people inapplicable seems to spike at seemingly random times (given that this is a panel data set, with the same households, I'm confused at this).

The variables I'm most confused about are religion_w8.oprlg1, oprlg, oprlg1_bh and oprlg5 - thanks for your help!